April 2002 Draft
JavaScript 2.0
Formal Description
Lexical Grammar
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Monday, November 26, 2001

This LALR(1) grammar describes the lexical syntax of the JavaScript 2.0 proposal. See also the description of the grammar notation.

This document is also available as a Word 98 rtf file.

The start symbols are: NextInputElementunit if the previous input element was a number; NextInputElementre if the previous input element was not a number and a / should be interpreted as a regular expression; and NextInputElementdiv if the previous input element was not a number and a / should be interpreted as a division or division-assignment operator.

Unicode Character Classes

UnicodeCharacter ⇒ Any Unicode character
UnicodeInitialAlphabetic ⇒ Any Unicode initial alphabetic character (includes ASCII A-Z and a-z)
UnicodeAlphanumeric ⇒ Any Unicode alphabetic or decimal digit character (includes ASCII 0-9, A-Z, and a-z)
WhiteSpaceCharacter ⇒
   «TAB» | «VT» | «FF» | «SP» | «u00A0»
|  «u2000» | «u2001» | «u2002» | «u2003» | «u2004» | «u2005» | «u2006» | «u2007»
|  «u2008» | «u2009» | «u200A» | «u200B»
|  «u3000»
LineTerminator ⇒ «LF» | «CR» | «u2028» | «u2029»
ASCIIDigit ⇒ 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Comments

LineComment ⇒ / / LineCommentCharacters
LineCommentCharacters ⇒
   «empty»
|  LineCommentCharacters NonTerminator
NonTerminator ⇒ UnicodeCharacter except LineTerminator
SingleLineBlockComment ⇒ / * BlockCommentCharacters * /
BlockCommentCharacters ⇒
   «empty»
|  BlockCommentCharacters NonTerminatorOrSlash
|  PreSlashCharacters /
PreSlashCharacters ⇒
   «empty»
|  BlockCommentCharacters NonTerminatorOrAsteriskOrSlash
|  PreSlashCharacters /
NonTerminatorOrSlash ⇒ NonTerminator except /
NonTerminatorOrAsteriskOrSlash ⇒ NonTerminator except * | /
MultiLineBlockComment ⇒ / * MultiLineBlockCommentCharacters BlockCommentCharacters * /
MultiLineBlockCommentCharacters ⇒
   BlockCommentCharacters LineTerminator
|  MultiLineBlockCommentCharacters BlockCommentCharacters LineTerminator

White Space

WhiteSpace ⇒
   «empty»
|  WhiteSpace WhiteSpaceCharacter
|  WhiteSpace SingleLineBlockComment

Line Breaks

LineBreak ⇒
   LineTerminator
|  LineComment LineTerminator
|  MultiLineBlockComment
LineBreaks ⇒
   LineBreak
|  LineBreaks WhiteSpace LineBreak

Input Elements

ν ∈ {re, div, unit}
NextInputElementre ⇒ WhiteSpace InputElementre
NextInputElementdiv ⇒ WhiteSpace InputElementdiv
NextInputElementunit ⇒
   [lookahead∉{ContinuingIdentifierCharacter, \}] WhiteSpace InputElementdiv
|  [lookahead∉{_}] IdentifierName
InputElementre ⇒
   LineBreaks
|  IdentifierOrKeyword
|  Punctuator
|  NumericLiteral
|  StringLiteral
|  RegExpLiteral
|  EndOfInput
InputElementdiv ⇒
   LineBreaks
|  IdentifierOrKeyword
|  Punctuator
|  DivisionPunctuator
|  NumericLiteral
|  StringLiteral
|  EndOfInput
EndOfInput ⇒
   End
|  LineComment End

Keywords and Identifiers

IdentifierName ⇒
   InitialIdentifierCharacterOrEscape
|  NullEscapes InitialIdentifierCharacterOrEscape
|  IdentifierName ContinuingIdentifierCharacterOrEscape
|  IdentifierName NullEscape
NullEscapes ⇒
   NullEscape
|  NullEscapes NullEscape
NullEscape ⇒ \ _
InitialIdentifierCharacterOrEscape ⇒
   InitialIdentifierCharacter
|  \ HexEscape
InitialIdentifierCharacter ⇒ UnicodeInitialAlphabetic | $ | _
ContinuingIdentifierCharacterOrEscape ⇒
   ContinuingIdentifierCharacter
|  \ HexEscape
ContinuingIdentifierCharacter ⇒ UnicodeAlphanumeric | $ | _
IdentifierOrKeyword ⇒ IdentifierName

Punctuators

Punctuator ⇒
   !
|  ! =
|  ! = =
|  %
|  % =
|  &
|  & &
|  & & =
|  & =
|  (
|  )
|  *
|  * =
|  +
|  + +
|  + =
|  ,
|  -
|  - -
|  - =
|  .
|  . . .
|  :
|  : :
|  ;
|  <
|  < <
|  < < =
|  < =
|  =
|  = =
|  = = =
|  >
|  > =
|  > >
|  > > =
|  > > >
|  > > > =
|  ?
|  [
|  ]
|  ^
|  ^ =
|  ^ ^
|  ^ ^ =
|  {
|  |
|  | =
|  | |
|  | | =
|  }
|  ~
DivisionPunctuator ⇒
   / [lookahead∉{/, *}]
|  / =

Numeric Literals

NumericLiteral ⇒
   DecimalLiteral
|  HexIntegerLiteral [lookahead∉{HexDigit}]
DecimalLiteral ⇒
   Mantissa
|  Mantissa LetterE SignedInteger
LetterE ⇒ E | e
Mantissa ⇒
   DecimalIntegerLiteral
|  DecimalIntegerLiteral .
|  DecimalIntegerLiteral . Fraction
|  . Fraction
DecimalIntegerLiteral ⇒
   0
|  NonZeroDecimalDigits
NonZeroDecimalDigits ⇒
   NonZeroDigit
|  NonZeroDecimalDigits ASCIIDigit
NonZeroDigit ⇒ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
Fraction ⇒ DecimalDigits
SignedInteger ⇒
   DecimalDigits
|  + DecimalDigits
|  - DecimalDigits
DecimalDigits ⇒
   ASCIIDigit
|  DecimalDigits ASCIIDigit
HexIntegerLiteral ⇒
   0 LetterX HexDigit
|  HexIntegerLiteral HexDigit
LetterX ⇒ X | x
HexDigit ⇒ 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | a | b | c | d | e | f

String Literals

θ ∈ {single, double}
StringLiteral ⇒
   ' StringCharssingle '
|  " StringCharsdouble "
StringCharsθ ⇒
   «empty»
|  StringCharsθ StringCharθ
|  StringCharsθ NullEscape
StringCharθ ⇒
   LiteralStringCharθ
|  \ StringEscape
LiteralStringCharsingle ⇒ UnicodeCharacter except ' | \ | LineTerminator
LiteralStringChardouble ⇒ UnicodeCharacter except " | \ | LineTerminator
StringEscape ⇒
   ControlEscape
|  ZeroEscape
|  HexEscape
|  IdentityEscape
IdentityEscape ⇒ NonTerminator except _ | UnicodeAlphanumeric
ControlEscape ⇒
   b
|  f
|  n
|  r
|  t
|  v
ZeroEscape ⇒ 0 [lookahead∉{ASCIIDigit}]
HexEscape ⇒
   x HexDigit HexDigit
|  u HexDigit HexDigit HexDigit HexDigit

Regular Expression Literals

RegExpLiteral ⇒ RegExpBody RegExpFlags
RegExpFlags ⇒
   «empty»
|  RegExpFlags ContinuingIdentifierCharacterOrEscape
|  RegExpFlags NullEscape
RegExpBody ⇒ / [lookahead∉{*}] RegExpChars /
RegExpChars ⇒
   RegExpChar
|  RegExpChars RegExpChar
RegExpChar ⇒
   OrdinaryRegExpChar
|  \ NonTerminator
OrdinaryRegExpChar ⇒ NonTerminator except \ | /
Waldemar Horwat
Last modified Monday, November 26, 2001
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