Syntax Color: Utilities

The "syntax-color" collection provides the underlying data structures and some helpful utilities for the color:text<%> class of the Framework: Racket GUI Application Framework.

1 Parenthesis Matching

Parenthesis matching code built on top of token-tree%.

2 Lexer Contract & the Don’t Stop struct

3 Racket Lexer

The racket-lexer function returns 5 values:

• Either a string containing the matching text or the eof object. Block comments and specials currently return an empty string. This may change in the future to other string or non-string data.

• A symbol in '(error comment sexp-comment white-space constant string no-color parenthesis hash-colon-keyword symbol eof other).

• A symbol in '(|(| |)| |[| |]| |{| |}|) or #f.

• A number representing the starting position of the match (or #f if eof).

• A number representing the ending position of the match (or #f if eof).

4 Default lexer

procedure (default-lexer in)   →   (or/c string? eof-object?) symbol? (or/c symbol? #f) (or/c number? #f) (or/c number? #f)

in : input-port?

A lexer that only identifies (, ), [, ], {, and } built specifically for color:text<%>.

default-lexer returns 5 values:

• Either a string containing the matching text or the eof object. Block specials currently return an empty string. This may change in the future to other string or non-string data.

• A symbol in '(comment white-space no-color eof).

• A symbol in '(|(| |)| |[| |]| |{| |}|) or #f.

• A number representing the starting position of the match (or #f if eof).

• A number representing the ending position of the match (or #f if eof).

5 Module Lexer

• The module-lexer function accepts an offset and lexer mode, instead of just an input port.

• In addition to the results of racket-lexer, module-lexer returns a backup distance and a new lexer mode.

• When mode is #f (indicating the start of the stream), the lexer checks in for a #lang specification.

  If a #lang line is present but the specified language does not exist, the entire in input is consumed and colored as 'error.

  If the language exists and the language provides a get-info function, then it is called with 'color-lexer. If the result is not #f, then it should be a lexer function for use with color:text<%>. The result mode is the lexer—paired with #f if the lexer is a procedure arity 3—so that future calls will dispatch to the language-supplied lexer.

  If the language is specified but it provides no get-info or 'color-lexer result, then racket-lexer is returned as the mode.

• When mode is a lexer procedure, the lexer is applied to in. The lexer’s results are returned, plus the lexer again as the mode.

• When mode is a pair, then the lexer procedure in the car is applied to in, offset, and the mode in the cdr. The lexer’s results are returned, except that its mode result is paired back with the lexer procedure.

6 Scribble Lexer

7 Splay Tree for Tokenization

This optimization is important for the colorer.