rascal

Adding Newline Character to Rascal Syntax Definition

How do I add a newline character as part of Rascal’s Syntax Definition. I tried this but it doesn’t seem work.

syntax Entity
   =  @Foldable entity: "entity" Id name  "{"  {Field “\n”}+ fields "}"
;

syntax Field 
   = field: Id name ":" Type t ;
Solution

  • Typically you would add a layout definition in scope, like so:

    layout Whitespace = [\ \n\t\r]* !>> [\ \n\t\r];

    After this is added, the other rules are augmented with the Whitespace non-terminal everywhere before the parser is generated.

    For example, internally Field+ becomes {Field Whitespace}+ en Field becomes Id name Whitespace ":" Whitespace Type t.

    So that adds Whitespace in between all the symbols. To be able to accept newlines and spaces also before and after the top-non-terminal add start to it:

    start syntax TranslationUnit = Entity*;

    This will add this rule automatically:

    syntax start[TranslationUnit] = Whitespace {Entity Whitespace}* Whitespace;