jashkenas--coffeescript/grammar.y

class Parser

# Declare tokens produced by the lexer
token IF ELSE THEN UNLESS
token NUMBER STRING REGEX
token TRUE FALSE NULL
token IDENTIFIER PROPERTY_ACCESS
token CODE PARAM NEW RETURN
token TRY CATCH FINALLY THROW
token BREAK CONTINUE
token FOR IN WHILE
token SWITCH CASE DEFAULT
token NEWLINE
token JS

prechigh
  nonassoc UMINUS NOT '!'
  left     '*' '/' '%'
  left     '+' '-'
  left     '<=' '<' '>' '>='
  right    '==' '!=' IS AINT
  left     '&&' '||' AND OR
  left     ':'
  right    '-=' '+=' '/=' '*='
  nonassoc IF
preclow

rule
  # All rules are declared in this format:
  #
  #   RuleName:
  #     OtherRule TOKEN AnotherRule    { code to run when this matches }
  #   | OtherRule                      { ... }
  #   ;
  #
  # In the code section (inside the {...} on the right):
  # - Assign to "result" the value returned by the rule.
  # - Use val[index of expression] to reference expressions on the left.


  # All parsing will end in this rule, being the trunk of the AST.
  Root:
    /* nothing */                     { result = Nodes.new([]) }
  | Terminator                        { result = Nodes.new([]) }
  | Expressions                       { result = val[0] }
  ;

  # Any list of expressions or method body, seperated by line breaks.
  Expressions:
    Expression                        { result = Nodes.new(val) }
  | Expressions Terminator Expression { result = val[0] << val[2] }
  | Expressions Terminator            { result = val[0] }
  | Terminator Expressions            { result = val[1] }
  ;

  # All types of expressions in our language
  Expression:
    Literal
  | Value
  | Call
  | Assign
  | Code
  | Operation
  | If
  | Try
  | Throw
  | Return
  | While
  | For
  | Switch
  ;

  # All tokens that can terminate an expression
  Terminator:
    "\n"
  | ";"
  ;

  # All tokens that can serve to begin the second block
  Then:
    THEN
  | Terminator
  ;

  # All hard-coded values
  Literal:
    NUMBER                            { result = LiteralNode.new(val[0]) }
  | STRING                            { result = LiteralNode.new(val[0]) }
  | JS                                { result = LiteralNode.new(val[0]) }
  | REGEX                             { result = LiteralNode.new(val[0]) }
  | TRUE                              { result = LiteralNode.new(true) }
  | FALSE                             { result = LiteralNode.new(false) }
  | NULL                              { result = LiteralNode.new(nil) }
  | BREAK                             { result = LiteralNode.new(val[0]) }
  | CONTINUE                          { result = LiteralNode.new(val[0]) }
  ;

  # Assign to a variable
  Assign:
    Value ":" Expression              { result = AssignNode.new(val[0], val[2]) }
  ;

  # Assignment within an object literal.
  AssignObj:
    IDENTIFIER ":" Expression         { result = AssignNode.new(val[0], val[2], :object) }
  ;

  # A Return statement.
  Return:
    RETURN Expression                 { result = ReturnNode.new(val[1]) }
  ;

  # Arithmetic and logical operators
  # For Ruby's Operator precedence, see:
  # https://www.cs.auckland.ac.nz/references/ruby/ProgrammingRuby/language.html
  Operation:
    '!' Expression                    { result = OpNode.new(val[0], val[1]) }
  | '-' Expression = UMINUS           { result = OpNode.new(val[0], val[1]) }
  | NOT Expression                    { result = OpNode.new(val[0], val[1]) }


  | Expression '*' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '/' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '%' Expression         { result = OpNode.new(val[1], val[0], val[2]) }

  | Expression '+' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '-' Expression         { result = OpNode.new(val[1], val[0], val[2]) }

  | Expression '<=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '<' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '>' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '>=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }

  | Expression '==' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '!=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression IS Expression          { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression AINT Expression        { result = OpNode.new(val[1], val[0], val[2]) }

  | Expression '&&' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '||' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression AND Expression         { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression OR Expression          { result = OpNode.new(val[1], val[0], val[2]) }

  | Expression '-=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '+=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '/=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '*=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '||=' Expression       { result = OpNode.new(val[1], val[0], val[2]) }
  | Expression '&&=' Expression       { result = OpNode.new(val[1], val[0], val[2]) }
  ;


  # Method definition
  Code:
    ParamList "=>" Expressions "."    { result = CodeNode.new(val[0], val[2]) }
  | "=>" Expressions "."              { result = CodeNode.new([], val[1]) }
  ;

  ParamList:
    PARAM                             { result = val }
  | ParamList "," PARAM               { result = val[0] << val[2] }
  ;

  Value:
    IDENTIFIER                        { result = ValueNode.new(val) }
  | Array                             { result = ValueNode.new(val) }
  | Object                            { result = ValueNode.new(val) }
  | Parenthetical                     { result = ValueNode.new(val) }
  | Value Accessor                    { result = val[0] << val[1] }
  | Invocation Accessor               { result = ValueNode.new(val[0], [val[1]]) }
  ;

  Accessor:
    PROPERTY_ACCESS IDENTIFIER        { result = AccessorNode.new(val[1]) }
  | Index                             { result = val[0] }
  ;

  Index:
    "[" Expression "]"                { result = IndexNode.new(val[1]) }
  ;

  Object:
    ObjectStart ObjectEnd             { result = ObjectNode.new([]) }
  | ObjectStart AssignList ObjectEnd  { result = ObjectNode.new(val[1]) }
  ;

  AssignList:
    /* nothing */                     { result = []}
  | AssignObj                         { result = val }
  | AssignList "," AssignObj          { result = val[0] << val[2] }
  | AssignList Terminator AssignObj   { result = val[0] << val[2] }
  ;

  # A method call.
  Call:
    Invocation                        { result = val[0] }
  | NEW Invocation                    { result = val[1].new_instance }
  ;

  Invocation:
    Value ParenStart ArgList ParenEnd { result = CallNode.new(val[0], val[2]) }
  ;

  # An Array.
  Array:
    ArrayStart ArgList ArrayEnd       { result = ArrayNode.new(val[1]) }
  ;

  # A list of arguments to a method call.
  ArgList:
    /* nothing */                     { result = [] }
  | Expression                        { result = val }
  | ArgList "," Expression            { result = val[0] << val[2] }
  | ArgList Terminator Expression     { result = val[0] << val[2] }
  ;

  If:
    IF Expression
       Then Expressions "."           { result = IfNode.new(val[1], val[3]) }
  | IF Expression
       Then Expressions
       ELSE Expressions "."           { result = IfNode.new(val[1], val[3], val[5]) }
  | Expression IF Expression          { result = IfNode.new(val[2], Nodes.new([val[0]])) }
  | Expression UNLESS Expression      { result = IfNode.new(val[2], Nodes.new([val[0]]), nil, :invert) }
  ;

  Try:
    TRY Expressions CATCH IDENTIFIER
      Expressions "."                 { result = TryNode.new(val[1], val[3], val[4]) }
  | TRY Expressions FINALLY
      Expressions "."                 { result = TryNode.new(val[1], nil, nil, val[3]) }
  | TRY Expressions CATCH IDENTIFIER
      Expressions
      FINALLY Expressions "."         { result = TryNode.new(val[1], val[3], val[4], val[6]) }
  ;

  Throw:
    THROW Expression                  { result = ThrowNode.new(val[1]) }
  ;

  Parenthetical:
    ParenStart Expressions ParenEnd   { result = ParentheticalNode.new(val[1]) }
  ;

  While:
    WHILE Expression Then
      Expressions "."                 { result = WhileNode.new(val[1], val[3]) }
  ;

  For:
  Expression FOR IDENTIFIER
    IN Expression "."                 { result = ForNode.new(val[0], val[4], val[2]) }
  | Expression FOR
      IDENTIFIER "," IDENTIFIER
      IN Expression "."               { result = ForNode.new(val[0], val[6], val[2], val[4]) }
  | Expression FOR IDENTIFIER
      IN Expression
      IF Expression "."               { result = ForNode.new(IfNode.new(val[6], Nodes.new([val[0]])), val[4], val[2]) }
  | Expression FOR
      IDENTIFIER "," IDENTIFIER
      IN Expression
      IF Expression "."               { result = ForNode.new(IfNode.new(val[8], Nodes.new([val[0]])), val[6], val[2], val[4]) }
  ;

  Switch:
    SWITCH Expression Then
      Cases "."                       { result = val[3].rewrite_condition(val[1]) }
  | SWITCH Expression Then
      Cases DEFAULT Expressions "."   { result = val[3].rewrite_condition(val[1]).add_default(val[5]) }
  ;

  Cases:
    Case                              { result = val[0] }
  | Cases Case                        { result = val[0] << val[1] }
  ;

  Case:
    CASE Expression Then Expressions  { result = IfNode.new(val[1], val[3]) }
  ;

  ObjectStart:
    "{"                               { result = nil }
  | "{" "\n"                          { result = nil }
  ;

  ObjectEnd:
    "}"                               { result = nil }
  | "\n" "}"                          { result = nil }
  ;

  ParenStart:
    "("                               { result = nil }
  | "(" "\n"                          { result = nil }
  ;

  ParenEnd:
    ")"                               { result = nil }
  | "\n" ")"                          { result = nil }
  ;

  ArrayStart:
    "["                               { result = nil }
  | "[" "\n"                          { result = nil }
  ;

  ArrayEnd:
    "]"                               { result = nil }
  | "\n" "]"                          { result = nil }
  ;

end

---- header
  require "lexer"
  require "nodes"

---- inner
  def parse(code, show_tokens=false)
    # @yydebug = true
    @tokens = Lexer.new.tokenize(code)
    puts @tokens.inspect if show_tokens
    do_parse
  end

  def next_token
    @tokens.shift
  end