How to match a variable to a token in javacc?

Question

I am trying to match a variable (a string) to one of my defined tokens in JAVACC. The pseudocode for what I am trying to do is...

String x;
if (x matches <FUNCTIONNAME>) {...}

How would I go about achieving this?

Thank you

Answer 1

Here is one way to do it. Use the STATIC==false option. The following code should do what you need

public boolean matches( String str, int k ) {
// Precondition:  k should be one of the integers
//   given a name in XXXConstants 
// Postcondition: result is true if and only if str would be lexed by
// the lexer as a single token of kind k possibly
// preceeded and followed by any number of skipped and special tokens.
    StringReader sr = new StringReader( str ) ;
    SimpleCharStream scs = new SimpleCharStream( sr ) ;
    XXXTokenManager lexer = new XXXTokenManager( scs );

    boolean matches = false ;
    try  { 
        Token a = lexer.getNextToken() ;
        Token b = lexer.getNextToken() ;
        matches = a.kind == k && b.kind == 0 ; }
    catch( Throwable t ) {}
    return matches ; 
}

One problem with this is that it will skip tokens declared as SKIP or SPECIAL_TOKEN. E.g. if I use a Java lexer then "/*hello*/\tworld // \n" will still match JavaParserConstants.ID. If you don't want this, you need to do two things. First go into the .jj file and convert any SKIP tokens to SPECIAL_TOKENS. Second add checks that there no special tokens were found

matches = a.kind == k && b.kind == 0 && a.specialToken == null && b.specialToken == null ;