Synopsis Disambiguation is the definition of filters on the parse trees that SyntaxDefinitions define. There are several ways of defining Disambiguation in Rascal.
Description There are generally three ways of removing ambiguity from parse forests that are produced by parsers generated from SyntaxDefinitions.
- The first way is to add disambiguation declarations to the SyntaxDefinition. You can choose from:
- Priority declarations, which can be used to define the relative priority in expression languages
- Associativity declarations, which can be used to define relative associativity between operators of expression languages
- Follow declarations, which can be used to implement longest match using lookahead
- Precede declarations, which can be used to implement first match using look behind
- Reserve declarations, which allow you to finite sets of strings from a SyntaxDefinition to implement keyword reservation
- The second way is to add Actions that will be triggered just after parsing and allow you to trim a parse forest using any information necessary.
- The third way is use the Visit statement on a parse tree and implement your own filter post-parsing time, or any other kind of program that processes ParseTrees.