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key_differences [2020/09/26 23:23] – [Streamlined Syntax] revuskykey_differences [2020/09/26 23:24] – revusky
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 JavaCC 21 incorporates an [[new syntax summary|alternative streamlined syntax]] that should be quite a bit more pleasant to write and easier to read. JavaCC 21 incorporates an [[new syntax summary|alternative streamlined syntax]] that should be quite a bit more pleasant to write and easier to read.
  
-===== More powerful lookahead ===== +The difference is frequently dramatic. Where the legacy tool required you to write things like:
- +
-Perhaps most importantly, the longstanding bug of nested syntactic lookahead not working correctly has [[https://javacc.com/2020/07/15/nested-syntactic-lookahead-works/|finally been squashed]]! +
- +
-The ''SCAN'' construct (designed to supersede the legacy ''LOOKAHEAD'') offers a superset of the legacy ''LOOKAHEAD'' functionality. [[Lookbehind]] predicates allow you to define conditions at [[choice points]] based on scanning backwards in the parse/lookahead stack. [[Lookbehind]] also works in arbitrarily nested scanahead. +
- +
-The new [[up to here]] construct should eliminate the need to write more verbose and error-prone numerical and syntactic lookahead constructs.  +
- +
-The combined effect of the new features is frequently dramatic. Where the legacy tool required you to write things like:+
  
 <code> <code>
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      Foo Bar =>|| Baz      Foo Bar =>|| Baz
 </code>          </code>         
 +
 +===== More powerful lookahead =====
 +
 +Perhaps most importantly, the longstanding bug of nested syntactic lookahead not working correctly has [[https://javacc.com/2020/07/15/nested-syntactic-lookahead-works/|finally been squashed]]!
 +
 +The ''SCAN'' construct (designed to supersede the legacy ''LOOKAHEAD'') offers a superset of the legacy ''LOOKAHEAD'' functionality. [[Lookbehind]] predicates allow you to define conditions at [[choice points]] based on scanning backwards in the parse/lookahead stack. [[Lookbehind]] also works in arbitrarily nested scanahead.
 +
 +The new [[up to here]] construct should eliminate the need to write more verbose and error-prone numerical and syntactic lookahead constructs. 
 +
 +