nodes.coffee

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nodes.coffee
¶

nodes.coffee contains all of the node classes for the syntax tree. Most nodes are created as the result of actions in the grammar, but some are created by other nodes as a method of code generation. To convert the syntax tree into a string of JavaScript code, call compile() on the root.
```
Error.stackTraceLimit = Infinity

{Scope} = require './scope'
{RESERVED, STRICT_PROSCRIBED} = require './lexer'
```

Import the helpers we plan to use.

{compact, flatten, extend, merge, del, starts, ends, last, some,
addLocationDataFn, locationDataToString, throwSyntaxError} = require './helpers'

Functions required by parser

exports.extend = extend
exports.addLocationDataFn = addLocationDataFn

Constant functions for nodes that don’t need customization.

YES     = -> yes
NO      = -> no
THIS    = -> this
NEGATE  = -> @negated = not @negated; this

¶

CodeFragment

The various nodes defined below all compile to a collection of CodeFragment objects. A CodeFragments is a block of generated code, and the location in the source file where the code came from. CodeFragments can be assembled together into working code just by catting together all the CodeFragments’ code snippets, in order.

exports.CodeFragment = class CodeFragment
  constructor: (parent, code) ->
    @code = "#{code}"
    @locationData = parent?.locationData
    @type = parent?.constructor?.name or 'unknown'

  toString:   ->
    "#{@code}#{if @locationData then ": " + locationDataToString(@locationData) else ''}"

Convert an array of CodeFragments into a string.

fragmentsToText = (fragments) ->
  (fragment.code for fragment in fragments).join('')

¶

Base
¶

The Base is the abstract base class for all nodes in the syntax tree. Each subclass implements the compileNode method, which performs the code generation for that node. To compile a node to JavaScript, call compile on it, which wraps compileNode in some generic extra smarts, to know when the generated code needs to be wrapped up in a closure. An options hash is passed and cloned throughout, containing information about the environment from higher in the tree (such as if a returned value is being requested by the surrounding function), information about the current scope, and indentation level.
```
exports.Base = class Base

  compile: (o, lvl) ->
    fragmentsToText @compileToFragments o, lvl
```
¶

Common logic for determining whether to wrap this node in a closure before compiling it, or to compile directly. We need to wrap if this node is a statement, and it’s not a pureStatement, and we’re not at the top level of a block (which would be unnecessary), and we haven’t already been asked to return the result (because statements know how to return results).
```
  compileToFragments: (o, lvl) ->
    o        = extend {}, o
    o.level  = lvl if lvl
    node     = @unfoldSoak(o) or this
    node.tab = o.indent
    if o.level is LEVEL_TOP or not node.isStatement(o)
      node.compileNode o
    else
      node.compileClosure o
```

Statements converted into expressions via closure-wrapping share a scope object with their parent closure, to preserve the expected lexical scope.

  compileClosure: (o) ->
    if jumpNode = @jumps()
      jumpNode.error 'cannot use a pure statement in an expression'
    o.sharedScope = yes
    func = new Code [], Block.wrap [this]
    args = []
    if (argumentsNode = @contains isLiteralArguments) or @contains isLiteralThis
      args = [new Literal 'this']
      if argumentsNode
        meth = 'apply'
        args.push new Literal 'arguments'
      else
        meth = 'call'
      func = new Value func, [new Access new Literal meth]
    (new Call func, args).compileNode o

If the code generation wishes to use the result of a complex expression in multiple places, ensure that the expression is only ever evaluated once, by assigning it to a temporary variable. Pass a level to precompile.

If level is passed, then returns [val, ref], where val is the compiled value, and ref is the compiled reference. If level is not passed, this returns [val, ref] where the two values are raw nodes which have not been compiled.

  cache: (o, level, reused) ->
    unless @isComplex()
      ref = if level then @compileToFragments o, level else this
      [ref, ref]
    else
      ref = new Literal reused or o.scope.freeVariable 'ref'
      sub = new Assign ref, this
      if level then [sub.compileToFragments(o, level), [@makeCode(ref.value)]] else [sub, ref]

  cacheToCodeFragments: (cacheValues) ->
    [fragmentsToText(cacheValues[0]), fragmentsToText(cacheValues[1])]

Construct a node that returns the current node’s result. Note that this is overridden for smarter behavior for many statement nodes (e.g. If, For)…

  makeReturn: (res) ->
    me = @unwrapAll()
    if res
      new Call new Literal("#{res}.push"), [me]
    else
      new Return me

¶

Does this node, or any of its children, contain a node of a certain kind? Recursively traverses down the children nodes and returns the first one that verifies pred. Otherwise return undefined. contains does not cross scope boundaries.
```
  contains: (pred) ->
    node = undefined
    @traverseChildren no, (n) ->
      if pred n
        node = n
        return no
    node
```

Pull out the last non-comment node of a node list.

  lastNonComment: (list) ->
    i = list.length
    return list[i] while i-- when list[i] not instanceof Comment
    null

toString representation of the node, for inspecting the parse tree. This is what coffee --nodes prints out.

  toString: (idt = '', name = @constructor.name) ->
    tree = '\n' + idt + name
    tree += '?' if @soak
    @eachChild (node) -> tree += node.toString idt + TAB
    tree

Passes each child to a function, breaking when the function returns false.

  eachChild: (func) ->
    return this unless @children
    for attr in @children when @[attr]
      for child in flatten [@[attr]]
        return this if func(child) is false
    this

  traverseChildren: (crossScope, func) ->
    @eachChild (child) ->
      recur = func(child)
      child.traverseChildren(crossScope, func) unless recur is no

  invert: ->
    new Op '!', this

  unwrapAll: ->
    node = this
    continue until node is node = node.unwrap()
    node

Default implementations of the common node properties and methods. Nodes will override these with custom logic, if needed.

  children: []

  isStatement     : NO
  jumps           : NO
  isComplex       : YES
  isChainable     : NO
  isAssignable    : NO

  unwrap     : THIS
  unfoldSoak : NO

¶

Is this node used to assign a certain variable?
```
  assigns: NO
```

For this node and all descendents, set the location data to locationData if the location data is not already set.

  updateLocationDataIfMissing: (locationData) ->
    return this if @locationData
    @locationData = locationData

    @eachChild (child) ->
      child.updateLocationDataIfMissing locationData

Throw a SyntaxError associated with this node’s location.

  error: (message) ->
    throwSyntaxError message, @locationData

  makeCode: (code) ->
    new CodeFragment this, code

  wrapInBraces: (fragments) ->
    [].concat @makeCode('('), fragments, @makeCode(')')

fragmentsList is an array of arrays of fragments. Each array in fragmentsList will be concatonated together, with joinStr added in between each, to produce a final flat array of fragments.

  joinFragmentArrays: (fragmentsList, joinStr) ->
    answer = []
    for fragments,i in fragmentsList
      if i then answer.push @makeCode joinStr
      answer = answer.concat fragments
    answer

¶

Block
¶

The block is the list of expressions that forms the body of an indented block of code — the implementation of a function, a clause in an if, switch, or try, and so on…
```
exports.Block = class Block extends Base
  constructor: (nodes) ->
    @expressions = compact flatten nodes or []

  children: ['expressions']
```

Tack an expression on to the end of this expression list.

  push: (node) ->
    @expressions.push node
    this

¶

Remove and return the last expression of this expression list.
```
  pop: ->
    @expressions.pop()
```

Add an expression at the beginning of this expression list.

  unshift: (node) ->
    @expressions.unshift node
    this

If this Block consists of just a single node, unwrap it by pulling it back out.

  unwrap: ->
    if @expressions.length is 1 then @expressions[0] else this

Is this an empty block of code?

  isEmpty: ->
    not @expressions.length

  isStatement: (o) ->
    for exp in @expressions when exp.isStatement o
      return yes
    no

  jumps: (o) ->
    for exp in @expressions
      return jumpNode if jumpNode = exp.jumps o

A Block node does not return its entire body, rather it ensures that the final expression is returned.

  makeReturn: (res) ->
    len = @expressions.length
    while len--
      expr = @expressions[len]
      if expr not instanceof Comment
        @expressions[len] = expr.makeReturn res
        @expressions.splice(len, 1) if expr instanceof Return and not expr.expression
        break
    this

A Block is the only node that can serve as the root.

  compileToFragments: (o = {}, level) ->
    if o.scope then super o, level else @compileRoot o

Compile all expressions within the Block body. If we need to return the result, and it’s an expression, simply return it. If it’s a statement, ask the statement to do so.

  compileNode: (o) ->
    @tab  = o.indent
    top   = o.level is LEVEL_TOP
    compiledNodes = []

    for node, index in @expressions

      node = node.unwrapAll()
      node = (node.unfoldSoak(o) or node)
      if node instanceof Block

This is a nested block. We don’t do anything special here like enclose it in a new scope; we just compile the statements in this block along with our own

        compiledNodes.push node.compileNode o
      else if top
        node.front = true
        fragments = node.compileToFragments o
        unless node.isStatement o
          fragments.unshift @makeCode "#{@tab}"
          fragments.push @makeCode ";"
        compiledNodes.push fragments
      else
        compiledNodes.push node.compileToFragments o, LEVEL_LIST
    if top
      if @spaced
        return [].concat @joinFragmentArrays(compiledNodes, '\n\n'), @makeCode("\n")
      else
        return @joinFragmentArrays(compiledNodes, '\n')
    if compiledNodes.length
      answer = @joinFragmentArrays(compiledNodes, ', ')
    else
      answer = [@makeCode "void 0"]
    if compiledNodes.length > 1 and o.level >= LEVEL_LIST then @wrapInBraces answer else answer

¶

If we happen to be the top-level Block, wrap everything in a safety closure, unless requested not to. It would be better not to generate them in the first place, but for now, clean up obvious double-parentheses.
```
  compileRoot: (o) ->
    o.indent  = if o.bare then '' else TAB
    o.level   = LEVEL_TOP
    @spaced   = yes
    o.scope   = new Scope null, this, null
```

Mark given local variables in the root scope as parameters so they don’t end up being declared on this block.

    o.scope.parameter name for name in o.locals or []
    prelude   = []
    unless o.bare
      preludeExps = for exp, i in @expressions
        break unless exp.unwrap() instanceof Comment
        exp
      rest = @expressions[preludeExps.length...]
      @expressions = preludeExps
      if preludeExps.length
        prelude = @compileNode merge(o, indent: '')
        prelude.push @makeCode "\n"
      @expressions = rest
    fragments = @compileWithDeclarations o
    return fragments if o.bare
    [].concat prelude, @makeCode("(function() {\n"), fragments, @makeCode("\n}).call(this);\n")

Compile the expressions body for the contents of a function, with declarations of all inner variables pushed up to the top.

  compileWithDeclarations: (o) ->
    fragments = []
    post = []
    for exp, i in @expressions
      exp = exp.unwrap()
      break unless exp instanceof Comment or exp instanceof Literal
    o = merge(o, level: LEVEL_TOP)
    if i
      rest = @expressions.splice i, 9e9
      [spaced,    @spaced] = [@spaced, no]
      [fragments, @spaced] = [@compileNode(o), spaced]
      @expressions = rest
    post = @compileNode o
    {scope} = o
    if scope.expressions is this
      declars = o.scope.hasDeclarations()
      assigns = scope.hasAssignments
      if declars or assigns
        fragments.push @makeCode '\n' if i
        fragments.push @makeCode "#{@tab}var "
        if declars
          fragments.push @makeCode scope.declaredVariables().join(', ')
        if assigns
          fragments.push @makeCode ",\n#{@tab + TAB}" if declars
          fragments.push @makeCode scope.assignedVariables().join(",\n#{@tab + TAB}")
        fragments.push @makeCode ";\n#{if @spaced then '\n' else ''}"
      else if fragments.length and post.length
        fragments.push @makeCode "\n"
    fragments.concat post

Wrap up the given nodes as a Block, unless it already happens to be one.

  @wrap: (nodes) ->
    return nodes[0] if nodes.length is 1 and nodes[0] instanceof Block
    new Block nodes

¶

Literal

Literals are static values that can be passed through directly into JavaScript without translation, such as: strings, numbers, true, false, null…

exports.Literal = class Literal extends Base
  constructor: (@value) ->

  makeReturn: ->
    if @isStatement() then this else super

  isAssignable: ->
    IDENTIFIER.test @value

  isStatement: ->
    @value in ['break', 'continue', 'debugger']

  isComplex: NO

  assigns: (name) ->
    name is @value

  jumps: (o) ->
    return this if @value is 'break' and not (o?.loop or o?.block)
    return this if @value is 'continue' and not o?.loop

  compileNode: (o) ->
    code = if @value is 'this'
      if o.scope.method?.bound then o.scope.method.context else @value
    else if @value.reserved
      "\"#{@value}\""
    else
      @value
    answer = if @isStatement() then "#{@tab}#{code};" else code
    [@makeCode answer]

  toString: ->
    ' "' + @value + '"'

class exports.Undefined extends Base
  isAssignable: NO
  isComplex: NO
  compileNode: (o) ->
    [@makeCode if o.level >= LEVEL_ACCESS then '(void 0)' else 'void 0']

class exports.Null extends Base
  isAssignable: NO
  isComplex: NO
  compileNode: -> [@makeCode "null"]

class exports.Bool extends Base
  isAssignable: NO
  isComplex: NO
  compileNode: -> [@makeCode @val]
  constructor: (@val) ->

¶

Return

A return is a pureStatement — wrapping it in a closure wouldn’t make sense.

exports.Return = class Return extends Base
  constructor: (expr) ->
    @expression = expr if expr and not expr.unwrap().isUndefined

  children: ['expression']

  isStatement:     YES
  makeReturn:      THIS
  jumps:           THIS

  compileToFragments: (o, level) ->
    expr = @expression?.makeReturn()
    if expr and expr not instanceof Return then expr.compileToFragments o, level else super o, level

  compileNode: (o) ->
    answer = []

TODO: If we call expression.compile() here twice, we’ll sometimes get back different results!

    answer.push @makeCode @tab + "return#{if @expression then " " else ""}"
    if @expression
      answer = answer.concat @expression.compileToFragments o, LEVEL_PAREN
    answer.push @makeCode ";"
    return answer

¶

Value

A value, variable or literal or parenthesized, indexed or dotted into, or vanilla.

exports.Value = class Value extends Base
  constructor: (base, props, tag) ->
    return base if not props and base instanceof Value
    @base       = base
    @properties = props or []
    @[tag]      = true if tag
    return this

  children: ['base', 'properties']

Add a property (or properties ) Access to the list.

  add: (props) ->
    @properties = @properties.concat props
    this

  hasProperties: ->
    !!@properties.length

  bareLiteral: (type) ->
    not @properties.length and @base instanceof type

Some boolean checks for the benefit of other nodes.

  isArray        : -> @bareLiteral(Arr)
  isRange        : -> @bareLiteral(Range)
  isComplex      : -> @hasProperties() or @base.isComplex()
  isAssignable   : -> @hasProperties() or @base.isAssignable()
  isSimpleNumber : -> @bareLiteral(Literal) and SIMPLENUM.test @base.value
  isString       : -> @bareLiteral(Literal) and IS_STRING.test @base.value
  isRegex        : -> @bareLiteral(Literal) and IS_REGEX.test @base.value
  isAtomic       : ->
    for node in @properties.concat @base
      return no if node.soak or node instanceof Call
    yes

  isNotCallable  : -> @isSimpleNumber() or @isString() or @isRegex() or
                      @isArray() or @isRange() or @isSplice() or @isObject()

  isStatement : (o)    -> not @properties.length and @base.isStatement o
  assigns     : (name) -> not @properties.length and @base.assigns name
  jumps       : (o)    -> not @properties.length and @base.jumps o

  isObject: (onlyGenerated) ->
    return no if @properties.length
    (@base instanceof Obj) and (not onlyGenerated or @base.generated)

  isSplice: ->
    last(@properties) instanceof Slice

  looksStatic: (className) ->
    @base.value is className and @properties.length and
      @properties[0].name?.value isnt 'prototype'

¶

The value can be unwrapped as its inner node, if there are no attached properties.
```
  unwrap: ->
    if @properties.length then this else @base
```

A reference has base part (this value) and name part. We cache them separately for compiling complex expressions. a()[b()] ?= c -> (_base = a())[_name = b()] ? _base[_name] = c

  cacheReference: (o) ->
    name = last @properties
    if @properties.length < 2 and not @base.isComplex() and not name?.isComplex()
      return [this, this]  # `a` `a.b`
    base = new Value @base, @properties[...-1]
    if base.isComplex()  # `a().b`
      bref = new Literal o.scope.freeVariable 'base'
      base = new Value new Parens new Assign bref, base
    return [base, bref] unless name  # `a()`
    if name.isComplex()  # `a[b()]`
      nref = new Literal o.scope.freeVariable 'name'
      name = new Index new Assign nref, name.index
      nref = new Index nref
    [base.add(name), new Value(bref or base.base, [nref or name])]

We compile a value to JavaScript by compiling and joining each property. Things get much more interesting if the chain of properties has soak operators ?. interspersed. Then we have to take care not to accidentally evaluate anything twice when building the soak chain.

  compileNode: (o) ->
    @base.front = @front
    props = @properties
    fragments = @base.compileToFragments o, (if props.length then LEVEL_ACCESS else null)
    if (@base instanceof Parens or props.length) and SIMPLENUM.test fragmentsToText fragments
      fragments.push @makeCode '.'
    for prop in props
      fragments.push (prop.compileToFragments o)...
    fragments

Unfold a soak into an If: a?.b -> a.b if a?

  unfoldSoak: (o) ->
    @unfoldedSoak ?= do =>
      if ifn = @base.unfoldSoak o
        ifn.body.properties.push @properties...
        return ifn
      for prop, i in @properties when prop.soak
        prop.soak = off
        fst = new Value @base, @properties[...i]
        snd = new Value @base, @properties[i..]
        if fst.isComplex()
          ref = new Literal o.scope.freeVariable 'ref'
          fst = new Parens new Assign ref, fst
          snd.base = ref
        return new If new Existence(fst), snd, soak: on
      no

¶

Comment

CoffeeScript passes through block comments as JavaScript block comments at the same position.

exports.Comment = class Comment extends Base
  constructor: (@comment) ->

  isStatement:     YES
  makeReturn:      THIS

  compileNode: (o, level) ->
    comment = @comment.replace /^(\s*)#/gm, "$1 *"
    code = "/*#{multident comment, @tab}#{if '\n' in comment then "\n#{@tab}" else ''} */"
    code = o.indent + code if (level or o.level) is LEVEL_TOP
    [@makeCode("\n"), @makeCode(code)]

¶

Call

Node for a function invocation. Takes care of converting super() calls into calls against the prototype’s function of the same name.

exports.Call = class Call extends Base
  constructor: (variable, @args = [], @soak) ->
    @isNew    = false
    @isSuper  = variable is 'super'
    @variable = if @isSuper then null else variable
    if variable instanceof Value and variable.isNotCallable()
      variable.error "literal is not a function"

  children: ['variable', 'args']

Tag this invocation as creating a new instance.

  newInstance: ->
    base = @variable?.base or @variable
    if base instanceof Call and not base.isNew
      base.newInstance()
    else
      @isNew = true
    this

Grab the reference to the superclass’s implementation of the current method.

  superReference: (o) ->
    method = o.scope.namedMethod()
    if method?.klass
      accesses = [new Access(new Literal '__super__')]
      accesses.push new Access new Literal 'constructor' if method.static
      accesses.push new Access new Literal method.name
      (new Value (new Literal method.klass), accesses).compile o
    else if method?.ctor
      "#{method.name}.__super__.constructor"
    else
      @error 'cannot call super outside of an instance method.'

The appropriate this value for a super call.

  superThis : (o) ->
    method = o.scope.method
    (method and not method.klass and method.context) or "this"

Soaked chained invocations unfold into if/else ternary structures.

  unfoldSoak: (o) ->
    if @soak
      if @variable
        return ifn if ifn = unfoldSoak o, this, 'variable'
        [left, rite] = new Value(@variable).cacheReference o
      else
        left = new Literal @superReference o
        rite = new Value left
      rite = new Call rite, @args
      rite.isNew = @isNew
      left = new Literal "typeof #{ left.compile o } === \"function\""
      return new If left, new Value(rite), soak: yes
    call = this
    list = []
    loop
      if call.variable instanceof Call
        list.push call
        call = call.variable
        continue
      break unless call.variable instanceof Value
      list.push call
      break unless (call = call.variable.base) instanceof Call
    for call in list.reverse()
      if ifn
        if call.variable instanceof Call
          call.variable = ifn
        else
          call.variable.base = ifn
      ifn = unfoldSoak o, call, 'variable'
    ifn

Compile a vanilla function call.

  compileNode: (o) ->
    @variable?.front = @front
    compiledArray = Splat.compileSplattedArray o, @args, true
    if compiledArray.length
      return @compileSplat o, compiledArray
    compiledArgs = []
    for arg, argIndex in @args
      if argIndex then compiledArgs.push @makeCode ", "
      compiledArgs.push (arg.compileToFragments o, LEVEL_LIST)...

    fragments = []
    if @isSuper
      preface = @superReference(o) + ".call(#{@superThis(o)}"
      if compiledArgs.length then preface += ", "
      fragments.push @makeCode preface
    else
      if @isNew then fragments.push @makeCode 'new '
      fragments.push @variable.compileToFragments(o, LEVEL_ACCESS)...
      fragments.push @makeCode "("
    fragments.push compiledArgs...
    fragments.push @makeCode ")"
    fragments

If you call a function with a splat, it’s converted into a JavaScript .apply() call to allow an array of arguments to be passed. If it’s a constructor, then things get real tricky. We have to inject an inner constructor in order to be able to pass the varargs.

splatArgs is an array of CodeFragments to put into the ‘apply’.

  compileSplat: (o, splatArgs) ->
    if @isSuper
      return [].concat @makeCode("#{ @superReference o }.apply(#{@superThis(o)}, "),
        splatArgs, @makeCode(")")

    if @isNew
      idt = @tab + TAB
      return [].concat @makeCode("""
        (function(func, args, ctor) {
        #{idt}ctor.prototype = func.prototype;
        #{idt}var child = new ctor, result = func.apply(child, args);
        #{idt}return Object(result) === result ? result : child;
        #{@tab}})("""),
        (@variable.compileToFragments o, LEVEL_LIST),
        @makeCode(", "), splatArgs, @makeCode(", function(){})")

    answer = []
    base = new Value @variable
    if (name = base.properties.pop()) and base.isComplex()
      ref = o.scope.freeVariable 'ref'
      answer = answer.concat @makeCode("(#{ref} = "),
        (base.compileToFragments o, LEVEL_LIST),
        @makeCode(")"),
        name.compileToFragments(o)
    else
      fun = base.compileToFragments o, LEVEL_ACCESS
      fun = @wrapInBraces fun if SIMPLENUM.test fragmentsToText fun
      if name
        ref = fragmentsToText fun
        fun.push (name.compileToFragments o)...
      else
        ref = 'null'
      answer = answer.concat fun
    answer = answer.concat @makeCode(".apply(#{ref}, "), splatArgs, @makeCode(")")

¶

Extends

Node to extend an object’s prototype with an ancestor object. After goog.inherits from the Closure Library.

exports.Extends = class Extends extends Base
  constructor: (@child, @parent) ->

  children: ['child', 'parent']

Hooks one constructor into another’s prototype chain.

  compileToFragments: (o) ->
    new Call(new Value(new Literal utility 'extends'), [@child, @parent]).compileToFragments o

¶

Access

A . access into a property of a value, or the :: shorthand for an access into the object’s prototype.

exports.Access = class Access extends Base
  constructor: (@name, tag) ->
    @name.asKey = yes
    @soak  = tag is 'soak'

  children: ['name']

  compileToFragments: (o) ->
    name = @name.compileToFragments o
    if IDENTIFIER.test fragmentsToText name
      name.unshift @makeCode "."
    else
      name.unshift @makeCode "["
      name.push @makeCode "]"
    name

  isComplex: NO

¶

Index

A [ ... ] indexed access into an array or object.

exports.Index = class Index extends Base
  constructor: (@index) ->

  children: ['index']

  compileToFragments: (o) ->
    [].concat @makeCode("["), @index.compileToFragments(o, LEVEL_PAREN), @makeCode("]")

  isComplex: ->
    @index.isComplex()

¶

Range

A range literal. Ranges can be used to extract portions (slices) of arrays, to specify a range for comprehensions, or as a value, to be expanded into the corresponding array of integers at runtime.

exports.Range = class Range extends Base

  children: ['from', 'to']

  constructor: (@from, @to, tag) ->
    @exclusive = tag is 'exclusive'
    @equals = if @exclusive then '' else '='

Compiles the range’s source variables — where it starts and where it ends. But only if they need to be cached to avoid double evaluation.

  compileVariables: (o) ->
    o = merge o, top: true
    [@fromC, @fromVar]  =  @cacheToCodeFragments @from.cache o, LEVEL_LIST
    [@toC, @toVar]      =  @cacheToCodeFragments @to.cache o, LEVEL_LIST
    [@step, @stepVar]   =  @cacheToCodeFragments step.cache o, LEVEL_LIST if step = del o, 'step'
    [@fromNum, @toNum]  = [@fromVar.match(NUMBER), @toVar.match(NUMBER)]
    @stepNum            = @stepVar.match(NUMBER) if @stepVar

¶

When compiled normally, the range returns the contents of the for loop needed to iterate over the values in the range. Used by comprehensions.
```
  compileNode: (o) ->
    @compileVariables o unless @fromVar
    return @compileArray(o) unless o.index
```

Set up endpoints.

    known    = @fromNum and @toNum
    idx      = del o, 'index'
    idxName  = del o, 'name'
    namedIndex = idxName and idxName isnt idx
    varPart  = "#{idx} = #{@fromC}"
    varPart += ", #{@toC}" if @toC isnt @toVar
    varPart += ", #{@step}" if @step isnt @stepVar
    [lt, gt] = ["#{idx} <#{@equals}", "#{idx} >#{@equals}"]

Generate the condition.

    condPart = if @stepNum
      if parseNum(@stepNum[0]) > 0 then "#{lt} #{@toVar}" else "#{gt} #{@toVar}"
    else if known
      [from, to] = [parseNum(@fromNum[0]), parseNum(@toNum[0])]
      if from <= to then "#{lt} #{to}" else "#{gt} #{to}"
    else
      cond = if @stepVar then "#{@stepVar} > 0" else "#{@fromVar} <= #{@toVar}"
      "#{cond} ? #{lt} #{@toVar} : #{gt} #{@toVar}"

Generate the step.

    stepPart = if @stepVar
      "#{idx} += #{@stepVar}"
    else if known
      if namedIndex
        if from <= to then "++#{idx}" else "--#{idx}"
      else
        if from <= to then "#{idx}++" else "#{idx}--"
    else
      if namedIndex
        "#{cond} ? ++#{idx} : --#{idx}"
      else
        "#{cond} ? #{idx}++ : #{idx}--"

    varPart  = "#{idxName} = #{varPart}" if namedIndex
    stepPart = "#{idxName} = #{stepPart}" if namedIndex

The final loop body.

    [@makeCode "#{varPart}; #{condPart}; #{stepPart}"]

When used as a value, expand the range into the equivalent array.

  compileArray: (o) ->
    if @fromNum and @toNum and Math.abs(@fromNum - @toNum) <= 20
      range = [+@fromNum..+@toNum]
      range.pop() if @exclusive
      return [@makeCode "[#{ range.join(', ') }]"]
    idt    = @tab + TAB
    i      = o.scope.freeVariable 'i'
    result = o.scope.freeVariable 'results'
    pre    = "\n#{idt}#{result} = [];"
    if @fromNum and @toNum
      o.index = i
      body    = fragmentsToText @compileNode o
    else
      vars    = "#{i} = #{@fromC}" + if @toC isnt @toVar then ", #{@toC}" else ''
      cond    = "#{@fromVar} <= #{@toVar}"
      body    = "var #{vars}; #{cond} ? #{i} <#{@equals} #{@toVar} : #{i} >#{@equals} #{@toVar}; #{cond} ? #{i}++ : #{i}--"
    post   = "{ #{result}.push(#{i}); }\n#{idt}return #{result};\n#{o.indent}"
    hasArgs = (node) -> node?.contains isLiteralArguments
    args   = ', arguments' if hasArgs(@from) or hasArgs(@to)
    [@makeCode "(function() {#{pre}\n#{idt}for (#{body})#{post}}).apply(this#{args ? ''})"]

¶

Slice
¶

An array slice literal. Unlike JavaScript’s Array#slice, the second parameter specifies the index of the end of the slice, just as the first parameter is the index of the beginning.
```
exports.Slice = class Slice extends Base

  children: ['range']

  constructor: (@range) ->
    super()
```
¶

We have to be careful when trying to slice through the end of the array, 9e9 is used because not all implementations respect undefined or 1/0. 9e9 should be safe because 9e9 > 2**32, the max array length.
```
  compileNode: (o) ->
    {to, from} = @range
    fromCompiled = from and from.compileToFragments(o, LEVEL_PAREN) or [@makeCode '0']
```

TODO: jwalton - move this into the ‘if’?

    if to
      compiled     = to.compileToFragments o, LEVEL_PAREN
      compiledText = fragmentsToText compiled
      if not (not @range.exclusive and +compiledText is -1)
        toStr = ', ' + if @range.exclusive
          compiledText
        else if SIMPLENUM.test compiledText
          "#{+compiledText + 1}"
        else
          compiled = to.compileToFragments o, LEVEL_ACCESS
          "+#{fragmentsToText compiled} + 1 || 9e9"
    [@makeCode ".slice(#{ fragmentsToText fromCompiled }#{ toStr or '' })"]

¶

Obj

An object literal, nothing fancy.

exports.Obj = class Obj extends Base
  constructor: (props, @generated = false) ->
    @objects = @properties = props or []

  children: ['properties']

  compileNode: (o) ->
    props = @properties
    return [@makeCode(if @front then '({})' else '{}')] unless props.length
    if @generated
      for node in props when node instanceof Value
        node.error 'cannot have an implicit value in an implicit object'
    idt         = o.indent += TAB
    lastNoncom  = @lastNonComment @properties
    answer = []
    for prop, i in props
      join = if i is props.length - 1
        ''
      else if prop is lastNoncom or prop instanceof Comment
        '\n'
      else
        ',\n'
      indent = if prop instanceof Comment then '' else idt
      if prop instanceof Assign and prop.variable instanceof Value and prop.variable.hasProperties()
        prop.variable.error 'Invalid object key'
      if prop instanceof Value and prop.this
        prop = new Assign prop.properties[0].name, prop, 'object'
      if prop not instanceof Comment
        if prop not instanceof Assign
          prop = new Assign prop, prop, 'object'
        (prop.variable.base or prop.variable).asKey = yes
      if indent then answer.push @makeCode indent
      answer.push prop.compileToFragments(o, LEVEL_TOP)...
      if join then answer.push @makeCode join
    answer.unshift @makeCode "{#{ props.length and '\n' }"
    answer.push @makeCode "#{ props.length and '\n' + @tab }}"
    if @front then @wrapInBraces answer else answer

  assigns: (name) ->
    for prop in @properties when prop.assigns name then return yes
    no

¶

Arr

An array literal.

exports.Arr = class Arr extends Base
  constructor: (objs) ->
    @objects = objs or []

  children: ['objects']

  compileNode: (o) ->
    return [@makeCode '[]'] unless @objects.length
    o.indent += TAB
    answer = Splat.compileSplattedArray o, @objects
    return answer if answer.length

    answer = []
    compiledObjs = (obj.compileToFragments o, LEVEL_LIST for obj in @objects)
    for fragments, index in compiledObjs
      if index
        answer.push @makeCode ", "
      answer.push fragments...
    if fragmentsToText(answer).indexOf('\n') >= 0
      answer.unshift @makeCode "[\n#{o.indent}"
      answer.push @makeCode "\n#{@tab}]"
    else
      answer.unshift @makeCode "["
      answer.push @makeCode "]"
    answer

  assigns: (name) ->
    for obj in @objects when obj.assigns name then return yes
    no

¶

Class

The CoffeeScript class definition. Initialize a Class with its name, an optional superclass, and a list of prototype property assignments.

exports.Class = class Class extends Base
  constructor: (@variable, @parent, @body = new Block) ->
    @boundFuncs = []
    @body.classBody = yes

  children: ['variable', 'parent', 'body']

Figure out the appropriate name for the constructor function of this class.

  determineName: ->
    return null unless @variable
    decl = if tail = last @variable.properties
      tail instanceof Access and tail.name.value
    else
      @variable.base.value
    if decl in STRICT_PROSCRIBED
      @variable.error "class variable name may not be #{decl}"
    decl and= IDENTIFIER.test(decl) and decl

For all this-references and bound functions in the class definition, this is the Class being constructed.

  setContext: (name) ->
    @body.traverseChildren false, (node) ->
      return false if node.classBody
      if node instanceof Literal and node.value is 'this'
        node.value    = name
      else if node instanceof Code
        node.klass    = name
        node.context  = name if node.bound

Ensure that all functions bound to the instance are proxied in the constructor.

  addBoundFunctions: (o) ->
    for bvar in @boundFuncs
      lhs = (new Value (new Literal "this"), [new Access bvar]).compile o
      @ctor.body.unshift new Literal "#{lhs} = #{utility 'bind'}(#{lhs}, this)"
    return

Merge the properties from a top-level object as prototypal properties on the class.

  addProperties: (node, name, o) ->
    props = node.base.properties[..]
    exprs = while assign = props.shift()
      if assign instanceof Assign
        base = assign.variable.base
        delete assign.context
        func = assign.value
        if base.value is 'constructor'
          if @ctor
            assign.error 'cannot define more than one constructor in a class'
          if func.bound
            assign.error 'cannot define a constructor as a bound function'
          if func instanceof Code
            assign = @ctor = func
          else
            @externalCtor = o.classScope.freeVariable 'class'
            assign = new Assign new Literal(@externalCtor), func
        else
          if assign.variable.this
            func.static = yes
          else
            assign.variable = new Value(new Literal(name), [(new Access new Literal 'prototype'), new Access base])
            if func instanceof Code and func.bound
              @boundFuncs.push base
              func.bound = no
      assign
    compact exprs

Walk the body of the class, looking for prototype properties to be converted and tagging static assignments.

  walkBody: (name, o) ->
    @traverseChildren false, (child) =>
      cont = true
      return false if child instanceof Class
      if child instanceof Block
        for node, i in exps = child.expressions
          if node instanceof Assign and node.variable.looksStatic name
            node.value.static = yes
          else if node instanceof Value and node.isObject(true)
            cont = false
            exps[i] = @addProperties node, name, o
        child.expressions = exps = flatten exps
      cont and child not instanceof Class

use strict (and other directives) must be the first expression statement(s) of a function body. This method ensures the prologue is correctly positioned above the constructor.

  hoistDirectivePrologue: ->
    index = 0
    {expressions} = @body
    ++index while (node = expressions[index]) and node instanceof Comment or
      node instanceof Value and node.isString()
    @directives = expressions.splice 0, index

Make sure that a constructor is defined for the class, and properly configured.

  ensureConstructor: (name) ->
    if not @ctor
      @ctor = new Code
      if @externalCtor
        @ctor.body.push new Literal "#{@externalCtor}.apply(this, arguments)"
      else if @parent
        @ctor.body.push new Literal "#{name}.__super__.constructor.apply(this, arguments)"
      @ctor.body.makeReturn()
      @body.expressions.unshift @ctor
    @ctor.ctor = @ctor.name = name
    @ctor.klass = null
    @ctor.noReturn = yes

Instead of generating the JavaScript string directly, we build up the equivalent syntax tree and compile that, in pieces. You can see the constructor, property assignments, and inheritance getting built out below.

  compileNode: (o) ->
    if jumpNode = @body.jumps()
      jumpNode.error 'Class bodies cannot contain pure statements'
    if argumentsNode = @body.contains isLiteralArguments
      argumentsNode.error "Class bodies shouldn't reference arguments"

    name  = @determineName() or '_Class'
    name  = "_#{name}" if name.reserved
    lname = new Literal name
    func  = new Code [], Block.wrap [@body]
    args  = []
    o.classScope = func.makeScope o.scope

    @hoistDirectivePrologue()
    @setContext name
    @walkBody name, o
    @ensureConstructor name
    @addBoundFunctions o
    @body.spaced = yes
    @body.expressions.push lname

    if @parent
      superClass = new Literal o.classScope.freeVariable 'super', no
      @body.expressions.unshift new Extends lname, superClass
      func.params.push new Param superClass
      args.push @parent

    @body.expressions.unshift @directives...

    klass = new Parens new Call func, args
    klass = new Assign @variable, klass if @variable
    klass.compileToFragments o

¶

Assign

The Assign is used to assign a local variable to value, or to set the property of an object — including within object literals.

exports.Assign = class Assign extends Base
  constructor: (@variable, @value, @context, options) ->
    @param = options and options.param
    @subpattern = options and options.subpattern
    forbidden = (name = @variable.unwrapAll().value) in STRICT_PROSCRIBED
    if forbidden and @context isnt 'object'
      @variable.error "variable name may not be \"#{name}\""

  children: ['variable', 'value']

  isStatement: (o) ->
    o?.level is LEVEL_TOP and @context? and "?" in @context

  assigns: (name) ->
    @[if @context is 'object' then 'value' else 'variable'].assigns name

  unfoldSoak: (o) ->
    unfoldSoak o, this, 'variable'

Compile an assignment, delegating to compilePatternMatch or compileSplice if appropriate. Keep track of the name of the base object we’ve been assigned to, for correct internal references. If the variable has not been seen yet within the current scope, declare it.

  compileNode: (o) ->
    if isValue = @variable instanceof Value
      return @compilePatternMatch o if @variable.isArray() or @variable.isObject()
      return @compileSplice       o if @variable.isSplice()
      return @compileConditional  o if @context in ['||=', '&&=', '?=']
      return @compileSpecialMath  o if @context in ['**=', '//=', '%%=']
    compiledName = @variable.compileToFragments o, LEVEL_LIST
    name = fragmentsToText compiledName
    unless @context
      varBase = @variable.unwrapAll()
      unless varBase.isAssignable()
        @variable.error "\"#{@variable.compile o}\" cannot be assigned"
      unless varBase.hasProperties?()
        if @param
          o.scope.add name, 'var'
        else
          o.scope.find name
    if @value instanceof Code and match = METHOD_DEF.exec name
      @value.klass = match[1] if match[2]
      @value.name  = match[3] ? match[4] ? match[5]
    val = @value.compileToFragments o, LEVEL_LIST
    return (compiledName.concat @makeCode(": "), val) if @context is 'object'
    answer = compiledName.concat @makeCode(" #{ @context or '=' } "), val
    if o.level <= LEVEL_LIST then answer else @wrapInBraces answer

Brief implementation of recursive pattern matching, when assigning array or object literals to a value. Peeks at their properties to assign inner names. See the ECMAScript Harmony Wiki for details.

  compilePatternMatch: (o) ->
    top       = o.level is LEVEL_TOP
    {value}   = this
    {objects} = @variable.base
    unless olen = objects.length
      code = value.compileToFragments o
      return if o.level >= LEVEL_OP then @wrapInBraces code else code
    isObject = @variable.isObject()
    if top and olen is 1 and (obj = objects[0]) not instanceof Splat

Unroll simplest cases: {v} = x -> v = x.v

      if obj instanceof Assign
        {variable: {base: idx}, value: obj} = obj
      else
        idx = if isObject
          if obj.this then obj.properties[0].name else obj
        else
          new Literal 0
      acc   = IDENTIFIER.test idx.unwrap().value or 0
      value = new Value value
      value.properties.push new (if acc then Access else Index) idx
      if obj.unwrap().value in RESERVED
        obj.error "assignment to a reserved word: #{obj.compile o}"
      return new Assign(obj, value, null, param: @param).compileToFragments o, LEVEL_TOP
    vvar     = value.compileToFragments o, LEVEL_LIST
    vvarText = fragmentsToText vvar
    assigns  = []
    expandedIdx = false

Make vvar into a simple variable if it isn’t already.

    if not IDENTIFIER.test(vvarText) or @variable.assigns(vvarText)
      assigns.push [@makeCode("#{ ref = o.scope.freeVariable 'ref' } = "), vvar...]
      vvar = [@makeCode ref]
      vvarText = ref
    for obj, i in objects

A regular array pattern-match.

      idx = i
      if isObject
        if obj instanceof Assign

A regular object pattern-match.

          {variable: {base: idx}, value: obj} = obj
        else

A shorthand {a, b, @c} = val pattern-match.

          if obj.base instanceof Parens
            [obj, idx] = new Value(obj.unwrapAll()).cacheReference o
          else
            idx = if obj.this then obj.properties[0].name else obj
      if not expandedIdx and obj instanceof Splat
        name = obj.name.unwrap().value
        obj = obj.unwrap()
        val = "#{olen} <= #{vvarText}.length ? #{ utility 'slice' }.call(#{vvarText}, #{i}"
        if rest = olen - i - 1
          ivar = o.scope.freeVariable 'i'
          val += ", #{ivar} = #{vvarText}.length - #{rest}) : (#{ivar} = #{i}, [])"
        else
          val += ") : []"
        val   = new Literal val
        expandedIdx = "#{ivar}++"
      else if not expandedIdx and obj instanceof Expansion
        if rest = olen - i - 1
          if rest is 1
            expandedIdx = "#{vvarText}.length - 1"
          else
            ivar = o.scope.freeVariable 'i'
            val = new Literal "#{ivar} = #{vvarText}.length - #{rest}"
            expandedIdx = "#{ivar}++"
            assigns.push val.compileToFragments o, LEVEL_LIST
        continue
      else
        name = obj.unwrap().value
        if obj instanceof Splat or obj instanceof Expansion
          obj.error "multiple splats/expansions are disallowed in an assignment"
        if typeof idx is 'number'
          idx = new Literal expandedIdx or idx
          acc = no
        else
          acc = isObject and IDENTIFIER.test idx.unwrap().value or 0
        val = new Value new Literal(vvarText), [new (if acc then Access else Index) idx]
      if name? and name in RESERVED
        obj.error "assignment to a reserved word: #{obj.compile o}"
      assigns.push new Assign(obj, val, null, param: @param, subpattern: yes).compileToFragments o, LEVEL_LIST
    assigns.push vvar unless top or @subpattern
    fragments = @joinFragmentArrays assigns, ', '
    if o.level < LEVEL_LIST then fragments else @wrapInBraces fragments

¶

When compiling a conditional assignment, take care to ensure that the operands are only evaluated once, even though we have to reference them more than once.
```
  compileConditional: (o) ->
    [left, right] = @variable.cacheReference o
```

Disallow conditional assignment of undefined variables.

    if not left.properties.length and left.base instanceof Literal and
           left.base.value != "this" and not o.scope.check left.base.value
      @variable.error "the variable \"#{left.base.value}\" can't be assigned with #{@context} because it has not been declared before"
    if "?" in @context
      o.isExistentialEquals = true
      new If(new Existence(left), right, type: 'if').addElse(new Assign(right, @value, '=')).compileToFragments o
    else
      fragments = new Op(@context[...-1], left, new Assign(right, @value, '=')).compileToFragments o
      if o.level <= LEVEL_LIST then fragments else @wrapInBraces fragments

Convert special math assignment operators like a **= b to the equivalent extended form a = a ** b and then compiles that.

  compileSpecialMath: (o) ->
    [left, right] = @variable.cacheReference o
    new Assign(left, new Op(@context[...-1], right, @value)).compileToFragments o

Compile the assignment from an array splice literal, using JavaScript’s Array#splice method.

  compileSplice: (o) ->
    {range: {from, to, exclusive}} = @variable.properties.pop()
    name = @variable.compile o
    if from
      [fromDecl, fromRef] = @cacheToCodeFragments from.cache o, LEVEL_OP
    else
      fromDecl = fromRef = '0'
    if to
      if from instanceof Value and from.isSimpleNumber() and
         to instanceof Value and to.isSimpleNumber()
        to = to.compile(o) - fromRef
        to += 1 unless exclusive
      else
        to = to.compile(o, LEVEL_ACCESS) + ' - ' + fromRef
        to += ' + 1' unless exclusive
    else
      to = "9e9"
    [valDef, valRef] = @value.cache o, LEVEL_LIST
    answer = [].concat @makeCode("[].splice.apply(#{name}, [#{fromDecl}, #{to}].concat("), valDef, @makeCode(")), "), valRef
    if o.level > LEVEL_TOP then @wrapInBraces answer else answer

¶

Code

A function definition. This is the only node that creates a new Scope. When for the purposes of walking the contents of a function body, the Code has no children — they’re within the inner scope.

exports.Code = class Code extends Base
  constructor: (params, body, tag) ->
    @params  = params or []
    @body    = body or new Block
    @bound   = tag is 'boundfunc'

  children: ['params', 'body']

  isStatement: -> !!@ctor

  jumps: NO

  makeScope: (parentScope) -> new Scope parentScope, @body, this

¶

Compilation creates a new scope unless explicitly asked to share with the outer scope. Handles splat parameters in the parameter list by peeking at the JavaScript arguments object. If the function is bound with the => arrow, generates a wrapper that saves the current value of this through a closure.
```
  compileNode: (o) ->

    if @bound and o.scope.method?.bound
      @context = o.scope.method.context
```

Handle bound functions early.

    if @bound and not @context
      @context = '_this'
      wrapper = new Code [new Param new Literal @context], new Block [this]
      boundfunc = new Call(wrapper, [new Literal 'this'])
      boundfunc.updateLocationDataIfMissing @locationData
      return boundfunc.compileNode(o)

    o.scope         = del(o, 'classScope') or @makeScope o.scope
    o.scope.shared  = del(o, 'sharedScope')
    o.indent        += TAB
    delete o.bare
    delete o.isExistentialEquals
    params = []
    exprs  = []
    for param in @params when param not instanceof Expansion
      o.scope.parameter param.asReference o
    for param in @params when param.splat or param instanceof Expansion
      for {name: p} in @params when param not instanceof Expansion
        if p.this then p = p.properties[0].name
        if p.value then o.scope.add p.value, 'var', yes
      splats = new Assign new Value(new Arr(p.asReference o for p in @params)),
                          new Value new Literal 'arguments'
      break
    for param in @params
      if param.isComplex()
        val = ref = param.asReference o
        val = new Op '?', ref, param.value if param.value
        exprs.push new Assign new Value(param.name), val, '=', param: yes
      else
        ref = param
        if param.value
          lit = new Literal ref.name.value + ' == null'
          val = new Assign new Value(param.name), param.value, '='
          exprs.push new If lit, val
      params.push ref unless splats
    wasEmpty = @body.isEmpty()
    exprs.unshift splats if splats
    @body.expressions.unshift exprs... if exprs.length
    for p, i in params
      params[i] = p.compileToFragments o
      o.scope.parameter fragmentsToText params[i]
    uniqs = []
    @eachParamName (name, node) ->
      node.error "multiple parameters named '#{name}'" if name in uniqs
      uniqs.push name
    @body.makeReturn() unless wasEmpty or @noReturn
    code  = 'function'
    code  += ' ' + @name if @ctor
    code  += '('
    answer = [@makeCode(code)]
    for p, i in params
      if i then answer.push @makeCode ", "
      answer.push p...
    answer.push @makeCode ') {'
    answer = answer.concat(@makeCode("\n"), @body.compileWithDeclarations(o), @makeCode("\n#{@tab}")) unless @body.isEmpty()
    answer.push @makeCode '}'

    return [@makeCode(@tab), answer...] if @ctor
    if @front or (o.level >= LEVEL_ACCESS) then @wrapInBraces answer else answer

  eachParamName: (iterator) ->
    param.eachName iterator for param in @params

¶

Short-circuit traverseChildren method to prevent it from crossing scope boundaries unless crossScope is true.
```
  traverseChildren: (crossScope, func) ->
    super(crossScope, func) if crossScope
```
¶

Param

A parameter in a function definition. Beyond a typical Javascript parameter, these parameters can also attach themselves to the context of the function, as well as be a splat, gathering up a group of parameters into an array.

exports.Param = class Param extends Base
  constructor: (@name, @value, @splat) ->
    if (name = @name.unwrapAll().value) in STRICT_PROSCRIBED
      @name.error "parameter name \"#{name}\" is not allowed"

  children: ['name', 'value']

  compileToFragments: (o) ->
    @name.compileToFragments o, LEVEL_LIST

  asReference: (o) ->
    return @reference if @reference
    node = @name
    if node.this
      node = node.properties[0].name
      if node.value.reserved
        node = new Literal o.scope.freeVariable node.value
    else if node.isComplex()
      node = new Literal o.scope.freeVariable 'arg'
    node = new Value node
    node = new Splat node if @splat
    node.updateLocationDataIfMissing @locationData
    @reference = node

  isComplex: ->
    @name.isComplex()

¶

Iterates the name or names of a Param. In a sense, a destructured parameter represents multiple JS parameters. This method allows to iterate them all. The iterator function will be called as iterator(name, node) where name is the name of the parameter and node is the AST node corresponding to that name.
```
  eachName: (iterator, name = @name)->
    atParam = (obj) ->
      node = obj.properties[0].name
      iterator node.value, node unless node.value.reserved
```

simple literals foo

    return iterator name.value, name if name instanceof Literal

at-params @foo

    return atParam name if name instanceof Value
    for obj in name.objects

assignments within destructured parameters {foo:bar}

      if obj instanceof Assign
        @eachName iterator, obj.value.unwrap()

splats within destructured parameters [xs...]

      else if obj instanceof Splat
        node = obj.name.unwrap()
        iterator node.value, node
      else if obj instanceof Value

destructured parameters within destructured parameters [{a}]

        if obj.isArray() or obj.isObject()
          @eachName iterator, obj.base

at-params within destructured parameters {@foo}

        else if obj.this
          atParam obj

simple destructured parameters {foo}

        else iterator obj.base.value, obj.base
      else if obj not instanceof Expansion
        obj.error "illegal parameter #{obj.compile()}"
    return

¶

Splat

A splat, either as a parameter to a function, an argument to a call, or as part of a destructuring assignment.

exports.Splat = class Splat extends Base

  children: ['name']

  isAssignable: YES

  constructor: (name) ->
    @name = if name.compile then name else new Literal name

  assigns: (name) ->
    @name.assigns name

  compileToFragments: (o) ->
    @name.compileToFragments o

  unwrap: -> @name

Utility function that converts an arbitrary number of elements, mixed with splats, to a proper array.

  @compileSplattedArray: (o, list, apply) ->
    index = -1
    continue while (node = list[++index]) and node not instanceof Splat
    return [] if index >= list.length
    if list.length is 1
      node = list[0]
      fragments = node.compileToFragments o, LEVEL_LIST
      return fragments if apply
      return [].concat node.makeCode("#{ utility 'slice' }.call("), fragments, node.makeCode(")")
    args = list[index..]
    for node, i in args
      compiledNode = node.compileToFragments o, LEVEL_LIST
      args[i] = if node instanceof Splat
      then [].concat node.makeCode("#{ utility 'slice' }.call("), compiledNode, node.makeCode(")")
      else [].concat node.makeCode("["), compiledNode, node.makeCode("]")
    if index is 0
      node = list[0]
      concatPart = (node.joinFragmentArrays args[1..], ', ')
      return args[0].concat node.makeCode(".concat("), concatPart, node.makeCode(")")
    base = (node.compileToFragments o, LEVEL_LIST for node in list[...index])
    base = list[0].joinFragmentArrays base, ', '
    concatPart = list[index].joinFragmentArrays args, ', '
    [].concat list[0].makeCode("["), base, list[index].makeCode("].concat("), concatPart, (last list).makeCode(")")

¶

Expansion

Used to skip values inside an array destructuring (pattern matching) or parameter list.

exports.Expansion = class Expansion extends Base

  isComplex: NO

  compileNode: (o) ->
    @error 'Expansion must be used inside a destructuring assignment or parameter list'

  asReference: (o) ->
    this

  eachName: (iterator) ->

¶

While

A while loop, the only sort of low-level loop exposed by CoffeeScript. From it, all other loops can be manufactured. Useful in cases where you need more flexibility or more speed than a comprehension can provide.

exports.While = class While extends Base
  constructor: (condition, options) ->
    @condition = if options?.invert then condition.invert() else condition
    @guard     = options?.guard

  children: ['condition', 'guard', 'body']

  isStatement: YES

  makeReturn: (res) ->
    if res
      super
    else
      @returns = not @jumps loop: yes
      this

  addBody: (@body) ->
    this

  jumps: ->
    {expressions} = @body
    return no unless expressions.length
    for node in expressions
      return jumpNode if jumpNode = node.jumps loop: yes
    no

The main difference from a JavaScript while is that the CoffeeScript while can be used as a part of a larger expression — while loops may return an array containing the computed result of each iteration.

  compileNode: (o) ->
    o.indent += TAB
    set      = ''
    {body}   = this
    if body.isEmpty()
      body = @makeCode ''
    else
      if @returns
        body.makeReturn rvar = o.scope.freeVariable 'results'
        set  = "#{@tab}#{rvar} = [];\n"
      if @guard
        if body.expressions.length > 1
          body.expressions.unshift new If (new Parens @guard).invert(), new Literal "continue"
        else
          body = Block.wrap [new If @guard, body] if @guard
      body = [].concat @makeCode("\n"), (body.compileToFragments o, LEVEL_TOP), @makeCode("\n#{@tab}")
    answer = [].concat @makeCode(set + @tab + "while ("), @condition.compileToFragments(o, LEVEL_PAREN),
      @makeCode(") {"), body, @makeCode("}")
    if @returns
      answer.push @makeCode "\n#{@tab}return #{rvar};"
    answer

¶

Op

Simple Arithmetic and logical operations. Performs some conversion from CoffeeScript operations into their JavaScript equivalents.

exports.Op = class Op extends Base
  constructor: (op, first, second, flip ) ->
    return new In first, second if op is 'in'
    if op is 'do'
      return @generateDo first
    if op is 'new'
      return first.newInstance() if first instanceof Call and not first.do and not first.isNew
      first = new Parens first   if first instanceof Code and first.bound or first.do
    @operator = CONVERSIONS[op] or op
    @first    = first
    @second   = second
    @flip     = !!flip
    return this

The map of conversions from CoffeeScript to JavaScript symbols.

  CONVERSIONS =
    '==': '==='
    '!=': '!=='
    'of': 'in'

The map of invertible operators.

  INVERSIONS =
    '!==': '==='
    '===': '!=='

  children: ['first', 'second']

  isSimpleNumber: NO

  isUnary: ->
    not @second

  isComplex: ->
    not (@isUnary() and @operator in ['+', '-']) or @first.isComplex()

Am I capable of Python-style comparison chaining?

  isChainable: ->
    @operator in ['<', '>', '>=', '<=', '===', '!==']

  invert: ->
    if @isChainable() and @first.isChainable()
      allInvertable = yes
      curr = this
      while curr and curr.operator
        allInvertable and= (curr.operator of INVERSIONS)
        curr = curr.first
      return new Parens(this).invert() unless allInvertable
      curr = this
      while curr and curr.operator
        curr.invert = !curr.invert
        curr.operator = INVERSIONS[curr.operator]
        curr = curr.first
      this
    else if op = INVERSIONS[@operator]
      @operator = op
      if @first.unwrap() instanceof Op
        @first.invert()
      this
    else if @second
      new Parens(this).invert()
    else if @operator is '!' and (fst = @first.unwrap()) instanceof Op and
                                  fst.operator in ['!', 'in', 'instanceof']
      fst
    else
      new Op '!', this

  unfoldSoak: (o) ->
    @operator in ['++', '--', 'delete'] and unfoldSoak o, this, 'first'

  generateDo: (exp) ->
    passedParams = []
    func = if exp instanceof Assign and (ref = exp.value.unwrap()) instanceof Code
      ref
    else
      exp
    for param in func.params or []
      if param.value
        passedParams.push param.value
        delete param.value
      else
        passedParams.push param
    call = new Call exp, passedParams
    call.do = yes
    call

  compileNode: (o) ->
    isChain = @isChainable() and @first.isChainable()

In chains, there’s no need to wrap bare obj literals in parens, as the chained expression is wrapped.

    @first.front = @front unless isChain
    if @operator is 'delete' and o.scope.check(@first.unwrapAll().value)
      @error 'delete operand may not be argument or var'
    if @operator in ['--', '++'] and @first.unwrapAll().value in STRICT_PROSCRIBED
      @error "cannot increment/decrement \"#{@first.unwrapAll().value}\""
    return @compileUnary     o if @isUnary()
    return @compileChain     o if isChain
    switch @operator
      when '?'  then @compileExistence o
      when '**' then @compilePower o
      when '//' then @compileFloorDivision o
      when '%%' then @compileModulo o
      else
        lhs = @first.compileToFragments o, LEVEL_OP
        rhs = @second.compileToFragments o, LEVEL_OP
        answer = [].concat lhs, @makeCode(" #{@operator} "), rhs
        if o.level <= LEVEL_OP then answer else @wrapInBraces answer

Mimic Python’s chained comparisons when multiple comparison operators are used sequentially. For example:

bin/coffee -e 'console.log 50 < 65 > 10'
true

  compileChain: (o) ->
    [@first.second, shared] = @first.second.cache o
    fst = @first.compileToFragments o, LEVEL_OP
    fragments = fst.concat @makeCode(" #{if @invert then '&&' else '||'} "),
      (shared.compileToFragments o), @makeCode(" #{@operator} "), (@second.compileToFragments o, LEVEL_OP)
    @wrapInBraces fragments

Keep reference to the left expression, unless this an existential assignment

  compileExistence: (o) ->
    if @first.isComplex()
      ref = new Literal o.scope.freeVariable 'ref'
      fst = new Parens new Assign ref, @first
    else
      fst = @first
      ref = fst
    new If(new Existence(fst), ref, type: 'if').addElse(@second).compileToFragments o

Compile a unary Op.

  compileUnary: (o) ->
    parts = []
    op = @operator
    parts.push [@makeCode op]
    if op is '!' and @first instanceof Existence
      @first.negated = not @first.negated
      return @first.compileToFragments o
    if o.level >= LEVEL_ACCESS
      return (new Parens this).compileToFragments o
    plusMinus = op in ['+', '-']
    parts.push [@makeCode(' ')] if op in ['new', 'typeof', 'delete'] or
                      plusMinus and @first instanceof Op and @first.operator is op
    if (plusMinus and @first instanceof Op) or (op is 'new' and @first.isStatement o)
      @first = new Parens @first
    parts.push @first.compileToFragments o, LEVEL_OP
    parts.reverse() if @flip
    @joinFragmentArrays parts, ''

  compilePower: (o) ->

Make a Math.pow call

    pow = new Value new Literal('Math'), [new Access new Literal 'pow']
    new Call(pow, [@first, @second]).compileToFragments o

  compileFloorDivision: (o) ->
    floor = new Value new Literal('Math'), [new Access new Literal 'floor']
    div = new Op '/', @first, @second
    new Call(floor, [div]).compileToFragments o

  compileModulo: (o) ->
    mod = new Value new Literal utility 'modulo'
    new Call(mod, [@first, @second]).compileToFragments o

  toString: (idt) ->
    super idt, @constructor.name + ' ' + @operator

In

exports.In = class In extends Base
  constructor: (@object, @array) ->

  children: ['object', 'array']

  invert: NEGATE

  compileNode: (o) ->
    if @array instanceof Value and @array.isArray() and @array.base.objects.length
      for obj in @array.base.objects when obj instanceof Splat
        hasSplat = yes
        break

compileOrTest only if we have an array literal with no splats

      return @compileOrTest o unless hasSplat
    @compileLoopTest o

  compileOrTest: (o) ->
    [sub, ref] = @object.cache o, LEVEL_OP
    [cmp, cnj] = if @negated then [' !== ', ' && '] else [' === ', ' || ']
    tests = []
    for item, i in @array.base.objects
      if i then tests.push @makeCode cnj
      tests = tests.concat (if i then ref else sub), @makeCode(cmp), item.compileToFragments(o, LEVEL_ACCESS)
    if o.level < LEVEL_OP then tests else @wrapInBraces tests

  compileLoopTest: (o) ->
    [sub, ref] = @object.cache o, LEVEL_LIST
    fragments = [].concat @makeCode(utility('indexOf') + ".call("), @array.compileToFragments(o, LEVEL_LIST),
      @makeCode(", "), ref, @makeCode(") " + if @negated then '< 0' else '>= 0')
    return fragments if fragmentsToText(sub) is fragmentsToText(ref)
    fragments = sub.concat @makeCode(', '), fragments
    if o.level < LEVEL_LIST then fragments else @wrapInBraces fragments

  toString: (idt) ->
    super idt, @constructor.name + if @negated then '!' else ''

¶

Try

A classic try/catch/finally block.

exports.Try = class Try extends Base
  constructor: (@attempt, @errorVariable, @recovery, @ensure) ->

  children: ['attempt', 'recovery', 'ensure']

  isStatement: YES

  jumps: (o) -> @attempt.jumps(o) or @recovery?.jumps(o)

  makeReturn: (res) ->
    @attempt  = @attempt .makeReturn res if @attempt
    @recovery = @recovery.makeReturn res if @recovery
    this

Compilation is more or less as you would expect — the finally clause is optional, the catch is not.

  compileNode: (o) ->
    o.indent  += TAB
    tryPart   = @attempt.compileToFragments o, LEVEL_TOP

    catchPart = if @recovery
      placeholder = new Literal '_error'
      @recovery.unshift new Assign @errorVariable, placeholder if @errorVariable
      [].concat @makeCode(" catch ("), placeholder.compileToFragments(o), @makeCode(") {\n"),
        @recovery.compileToFragments(o, LEVEL_TOP), @makeCode("\n#{@tab}}")
    else unless @ensure or @recovery
      [@makeCode(' catch (_error) {}')]
    else
      []

    ensurePart = if @ensure then ([].concat @makeCode(" finally {\n"), @ensure.compileToFragments(o, LEVEL_TOP),
      @makeCode("\n#{@tab}}")) else []

    [].concat @makeCode("#{@tab}try {\n"),
      tryPart,
      @makeCode("\n#{@tab}}"), catchPart, ensurePart

¶

Throw

Simple node to throw an exception.

exports.Throw = class Throw extends Base
  constructor: (@expression) ->

  children: ['expression']

  isStatement: YES
  jumps:       NO

A Throw is already a return, of sorts…

  makeReturn: THIS

  compileNode: (o) ->
    [].concat @makeCode(@tab + "throw "), @expression.compileToFragments(o), @makeCode(";")

¶

Existence

Checks a variable for existence — not null and not undefined. This is similar to .nil? in Ruby, and avoids having to consult a JavaScript truth table.

exports.Existence = class Existence extends Base
  constructor: (@expression) ->

  children: ['expression']

  invert: NEGATE

  compileNode: (o) ->
    @expression.front = @front
    code = @expression.compile o, LEVEL_OP
    if IDENTIFIER.test(code) and not o.scope.check code
      [cmp, cnj] = if @negated then ['===', '||'] else ['!==', '&&']
      code = "typeof #{code} #{cmp} \"undefined\" #{cnj} #{code} #{cmp} null"
    else

do not use strict equality here; it will break existing code

      code = "#{code} #{if @negated then '==' else '!='} null"
    [@makeCode(if o.level <= LEVEL_COND then code else "(#{code})")]

¶

Parens

An extra set of parentheses, specified explicitly in the source. At one time we tried to clean up the results by detecting and removing redundant parentheses, but no longer — you can put in as many as you please.

Parentheses are a good way to force any statement to become an expression.

exports.Parens = class Parens extends Base
  constructor: (@body) ->

  children: ['body']

  unwrap    : -> @body
  isComplex : -> @body.isComplex()

  compileNode: (o) ->
    expr = @body.unwrap()
    if expr instanceof Value and expr.isAtomic()
      expr.front = @front
      return expr.compileToFragments o
    fragments = expr.compileToFragments o, LEVEL_PAREN
    bare = o.level < LEVEL_OP and (expr instanceof Op or expr instanceof Call or
      (expr instanceof For and expr.returns))
    if bare then fragments else @wrapInBraces fragments

¶

For

CoffeeScript’s replacement for the for loop is our array and object comprehensions, that compile into for loops here. They also act as an expression, able to return the result of each filtered iteration.

Unlike Python array comprehensions, they can be multi-line, and you can pass the current index of the loop as a second parameter. Unlike Ruby blocks, you can map and filter in a single pass.

exports.For = class For extends While
  constructor: (body, source) ->
    {@source, @guard, @step, @name, @index} = source
    @body    = Block.wrap [body]
    @own     = !!source.own
    @object  = !!source.object
    [@name, @index] = [@index, @name] if @object
    @index.error 'index cannot be a pattern matching expression' if @index instanceof Value
    @range   = @source instanceof Value and @source.base instanceof Range and not @source.properties.length
    @pattern = @name instanceof Value
    @index.error 'indexes do not apply to range loops' if @range and @index
    @name.error 'cannot pattern match over range loops' if @range and @pattern
    @name.error 'cannot use own with for-in' if @own and not @object
    @returns = false

  children: ['body', 'source', 'guard', 'step']

Welcome to the hairiest method in all of CoffeeScript. Handles the inner loop, filtering, stepping, and result saving for array, object, and range comprehensions. Some of the generated code can be shared in common, and some cannot.

  compileNode: (o) ->
    body      = Block.wrap [@body]
    lastJumps = last(body.expressions)?.jumps()
    @returns  = no if lastJumps and lastJumps instanceof Return
    source    = if @range then @source.base else @source
    scope     = o.scope
    name      = @name  and (@name.compile o, LEVEL_LIST) if not @pattern
    index     = @index and (@index.compile o, LEVEL_LIST)
    scope.find(name)  if name and not @pattern
    scope.find(index) if index
    rvar      = scope.freeVariable 'results' if @returns
    ivar      = (@object and index) or scope.freeVariable 'i'
    kvar      = (@range and name) or index or ivar
    kvarAssign = if kvar isnt ivar then "#{kvar} = " else ""
    if @step and not @range
      [step, stepVar] = @cacheToCodeFragments @step.cache o, LEVEL_LIST
      stepNum = stepVar.match NUMBER
    name      = ivar if @pattern
    varPart   = ''
    guardPart = ''
    defPart   = ''
    idt1      = @tab + TAB
    if @range
      forPartFragments = source.compileToFragments merge(o, {index: ivar, name, @step})
    else
      svar    = @source.compile o, LEVEL_LIST
      if (name or @own) and not IDENTIFIER.test svar
        defPart    += "#{@tab}#{ref = scope.freeVariable 'ref'} = #{svar};\n"
        svar       = ref
      if name and not @pattern
        namePart   = "#{name} = #{svar}[#{kvar}]"
      if not @object
        defPart += "#{@tab}#{step};\n" if step isnt stepVar
        lvar = scope.freeVariable 'len' unless @step and stepNum and down = (parseNum(stepNum[0]) < 0)
        declare = "#{kvarAssign}#{ivar} = 0, #{lvar} = #{svar}.length"
        declareDown = "#{kvarAssign}#{ivar} = #{svar}.length - 1"
        compare = "#{ivar} < #{lvar}"
        compareDown = "#{ivar} >= 0"
        if @step
          if stepNum
            if down
              compare = compareDown
              declare = declareDown
          else
            compare = "#{stepVar} > 0 ? #{compare} : #{compareDown}"
            declare = "(#{stepVar} > 0 ? (#{declare}) : #{declareDown})"
          increment = "#{ivar} += #{stepVar}"
        else
          increment = "#{if kvar isnt ivar then "++#{ivar}" else "#{ivar}++"}"
        forPartFragments  = [@makeCode("#{declare}; #{compare}; #{kvarAssign}#{increment}")]
    if @returns
      resultPart   = "#{@tab}#{rvar} = [];\n"
      returnResult = "\n#{@tab}return #{rvar};"
      body.makeReturn rvar
    if @guard
      if body.expressions.length > 1
        body.expressions.unshift new If (new Parens @guard).invert(), new Literal "continue"
      else
        body = Block.wrap [new If @guard, body] if @guard
    if @pattern
      body.expressions.unshift new Assign @name, new Literal "#{svar}[#{kvar}]"
    defPartFragments = [].concat @makeCode(defPart), @pluckDirectCall(o, body)
    varPart = "\n#{idt1}#{namePart};" if namePart
    if @object
      forPartFragments   = [@makeCode("#{kvar} in #{svar}")]
      guardPart = "\n#{idt1}if (!#{utility 'hasProp'}.call(#{svar}, #{kvar})) continue;" if @own
    bodyFragments = body.compileToFragments merge(o, indent: idt1), LEVEL_TOP
    if bodyFragments and (bodyFragments.length > 0)
      bodyFragments = [].concat @makeCode("\n"), bodyFragments, @makeCode("\n")
    [].concat defPartFragments, @makeCode("#{resultPart or ''}#{@tab}for ("),
      forPartFragments, @makeCode(") {#{guardPart}#{varPart}"), bodyFragments,
      @makeCode("#{@tab}}#{returnResult or ''}")

  pluckDirectCall: (o, body) ->
    defs = []
    for expr, idx in body.expressions
      expr = expr.unwrapAll()
      continue unless expr instanceof Call
      val = expr.variable?.unwrapAll()
      continue unless (val instanceof Code) or
                      (val instanceof Value and
                      val.base?.unwrapAll() instanceof Code and
                      val.properties.length is 1 and
                      val.properties[0].name?.value in ['call', 'apply'])
      fn    = val.base?.unwrapAll() or val
      ref   = new Literal o.scope.freeVariable 'fn'
      base  = new Value ref
      if val.base
        [val.base, base] = [base, val]
      body.expressions[idx] = new Call base, expr.args
      defs = defs.concat @makeCode(@tab), (new Assign(ref, fn).compileToFragments(o, LEVEL_TOP)), @makeCode(';\n')
    defs

¶

Switch

A JavaScript switch statement. Converts into a returnable expression on-demand.

exports.Switch = class Switch extends Base
  constructor: (@subject, @cases, @otherwise) ->

  children: ['subject', 'cases', 'otherwise']

  isStatement: YES

  jumps: (o = {block: yes}) ->
    for [conds, block] in @cases
      return jumpNode if jumpNode = block.jumps o
    @otherwise?.jumps o

  makeReturn: (res) ->
    pair[1].makeReturn res for pair in @cases
    @otherwise or= new Block [new Literal 'void 0'] if res
    @otherwise?.makeReturn res
    this

  compileNode: (o) ->
    idt1 = o.indent + TAB
    idt2 = o.indent = idt1 + TAB
    fragments = [].concat @makeCode(@tab + "switch ("),
      (if @subject then @subject.compileToFragments(o, LEVEL_PAREN) else @makeCode "false"),
      @makeCode(") {\n")
    for [conditions, block], i in @cases
      for cond in flatten [conditions]
        cond  = cond.invert() unless @subject
        fragments = fragments.concat @makeCode(idt1 + "case "), cond.compileToFragments(o, LEVEL_PAREN), @makeCode(":\n")
      fragments = fragments.concat body, @makeCode('\n') if (body = block.compileToFragments o, LEVEL_TOP).length > 0
      break if i is @cases.length - 1 and not @otherwise
      expr = @lastNonComment block.expressions
      continue if expr instanceof Return or (expr instanceof Literal and expr.jumps() and expr.value isnt 'debugger')
      fragments.push cond.makeCode(idt2 + 'break;\n')
    if @otherwise and @otherwise.expressions.length
      fragments.push @makeCode(idt1 + "default:\n"), (@otherwise.compileToFragments o, LEVEL_TOP)..., @makeCode("\n")
    fragments.push @makeCode @tab + '}'
    fragments

¶

If

If/else statements. Acts as an expression by pushing down requested returns to the last line of each clause.

Single-expression Ifs are compiled into conditional operators if possible, because ternaries are already proper expressions, and don’t need conversion.

exports.If = class If extends Base
  constructor: (condition, @body, options = {}) ->
    @condition = if options.type is 'unless' then condition.invert() else condition
    @elseBody  = null
    @isChain   = false
    {@soak}    = options

  children: ['condition', 'body', 'elseBody']

  bodyNode:     -> @body?.unwrap()
  elseBodyNode: -> @elseBody?.unwrap()

Rewrite a chain of Ifs to add a default case as the final else.

  addElse: (elseBody) ->
    if @isChain
      @elseBodyNode().addElse elseBody
    else
      @isChain  = elseBody instanceof If
      @elseBody = @ensureBlock elseBody
      @elseBody.updateLocationDataIfMissing elseBody.locationData
    this

The If only compiles into a statement if either of its bodies needs to be a statement. Otherwise a conditional operator is safe.

  isStatement: (o) ->
    o?.level is LEVEL_TOP or
      @bodyNode().isStatement(o) or @elseBodyNode()?.isStatement(o)

  jumps: (o) -> @body.jumps(o) or @elseBody?.jumps(o)

  compileNode: (o) ->
    if @isStatement o then @compileStatement o else @compileExpression o

  makeReturn: (res) ->
    @elseBody  or= new Block [new Literal 'void 0'] if res
    @body     and= new Block [@body.makeReturn res]
    @elseBody and= new Block [@elseBody.makeReturn res]
    this

  ensureBlock: (node) ->
    if node instanceof Block then node else new Block [node]

Compile the If as a regular if-else statement. Flattened chains force inner else bodies into statement form.

  compileStatement: (o) ->
    child    = del o, 'chainChild'
    exeq     = del o, 'isExistentialEquals'

    if exeq
      return new If(@condition.invert(), @elseBodyNode(), type: 'if').compileToFragments o

    indent   = o.indent + TAB
    cond     = @condition.compileToFragments o, LEVEL_PAREN
    body     = @ensureBlock(@body).compileToFragments merge o, {indent}
    ifPart   = [].concat @makeCode("if ("), cond, @makeCode(") {\n"), body, @makeCode("\n#{@tab}}")
    ifPart.unshift @makeCode @tab unless child
    return ifPart unless @elseBody
    answer = ifPart.concat @makeCode(' else ')
    if @isChain
      o.chainChild = yes
      answer = answer.concat @elseBody.unwrap().compileToFragments o, LEVEL_TOP
    else
      answer = answer.concat @makeCode("{\n"), @elseBody.compileToFragments(merge(o, {indent}), LEVEL_TOP), @makeCode("\n#{@tab}}")
    answer

Compile the If as a conditional operator.

  compileExpression: (o) ->
    cond = @condition.compileToFragments o, LEVEL_COND
    body = @bodyNode().compileToFragments o, LEVEL_LIST
    alt  = if @elseBodyNode() then @elseBodyNode().compileToFragments(o, LEVEL_LIST) else [@makeCode('void 0')]
    fragments = cond.concat @makeCode(" ? "), body, @makeCode(" : "), alt
    if o.level >= LEVEL_COND then @wrapInBraces fragments else fragments

  unfoldSoak: ->
    @soak and this

¶

Constants
¶
```
UTILITIES =
```

Correctly set up a prototype chain for inheritance, including a reference to the superclass for super() calls, and copies of any static properties.

  extends: -> "
    function(child, parent) {
      for (var key in parent) {
        if (#{utility 'hasProp'}.call(parent, key)) child[key] = parent[key];
      }
      function ctor() {
        this.constructor = child;
      }
      ctor.prototype = parent.prototype;
      child.prototype = new ctor();
      child.__super__ = parent.prototype;
      return child;
    }
  "

Create a function bound to the current value of “this”.

  bind: -> '
    function(fn, me){
      return function(){
        return fn.apply(me, arguments);
      };
    }
  '

Discover if an item is in an array.

  indexOf: -> "
    [].indexOf || function(item) {
      for (var i = 0, l = this.length; i < l; i++) {
        if (i in this && this[i] === item) return i;
      }
      return -1;
    }
  "

  modulo: -> """
    function(a, b) { return (a % b + +b) % b; }
  """

Shortcuts to speed up the lookup time for native functions.

  hasProp: -> '{}.hasOwnProperty'
  slice  : -> '[].slice'

Levels indicate a node’s position in the AST. Useful for knowing if parens are necessary or superfluous.

LEVEL_TOP    = 1  # ...;
LEVEL_PAREN  = 2  # (...)
LEVEL_LIST   = 3  # [...]
LEVEL_COND   = 4  # ... ? x : y
LEVEL_OP     = 5  # !...
LEVEL_ACCESS = 6  # ...[0]

Tabs are two spaces for pretty printing.

TAB = '  '

IDENTIFIER_STR = "[$A-Za-z_\\x7f-\\uffff][$\\w\\x7f-\\uffff]*"
IDENTIFIER = /// ^ #{IDENTIFIER_STR} $ ///
SIMPLENUM  = /^[+-]?\d+$/
HEXNUM = /^[+-]?0x[\da-f]+/i
NUMBER    = ///^[+-]?(?:
  0x[\da-f]+ |              # hex
  \d*\.?\d+ (?:e[+-]?\d+)?  # decimal
)$///i

METHOD_DEF = /// ^
  (#{IDENTIFIER_STR})
  (\.prototype)?
  (?: \.(#{IDENTIFIER_STR})
    | \[("(?:[^\\"\r\n]|\\.)*"|'(?:[^\\'\r\n]|\\.)*')\]
    | \[(0x[\da-fA-F]+ | \d*\.?\d+ (?:[eE][+-]?\d+)?)\]
  )
$ ///

¶

Is a literal value a string/regex?
```
IS_STRING = /^['"]/
IS_REGEX = /^\//
```
¶

Helper Functions
¶

Helper for ensuring that utility functions are assigned at the top level.

utility = (name) ->
  ref = "__#{name}"
  Scope.root.assign ref, UTILITIES[name]()
  ref

multident = (code, tab) ->
  code = code.replace /\n/g, '$&' + tab
  code.replace /\s+$/, ''

Parse a number (+- decimal/hexadecimal) Examples: 0, -1, 1, 2e3, 2e-3, -0xfe, 0xfe

parseNum = (x) ->
  if not x?
    0
  else if x.match HEXNUM
    parseInt x, 16
  else
    parseFloat x

isLiteralArguments = (node) ->
  node instanceof Literal and node.value is 'arguments' and not node.asKey

isLiteralThis = (node) ->
  (node instanceof Literal and node.value is 'this' and not node.asKey) or
    (node instanceof Code and node.bound) or
    (node instanceof Call and node.isSuper)

Unfold a node’s child if soak, then tuck the node under created If

unfoldSoak = (o, parent, name) ->
  return unless ifn = parent[name].unfoldSoak o
  parent[name] = ifn.body
  ifn.body = new Value parent
  ifn

nodes.coffee

CodeFragment

Base

Block

Literal

Return

Value

Comment

Call

Extends

Access

Index

Range

Slice

Obj

Arr

Class

Assign

Code

Param

Splat

Expansion

While

Op

In

Try

Throw

Existence

Parens

For

Switch

If

Constants

Helper Functions