Scheme mode ; See if the input starts with a given symbol. (define (match-symbol input pattern) (cond ((null? (remain input)) #f) ((eqv? (car (remain input)) pattern) (r-cdr input)) (else #f))) ; Allow the input to start with one of a list of patterns. (define (match-or input pattern) (cond ((null? pattern) #f) ((match-pattern input (car pattern))) (else (match-or input (cdr pattern))))) ; Allow a sequence of patterns. (define (match-seq input pattern) (if (null? pattern) input (let ((match (match-pattern input (car pattern)))) (if match (match-seq match (cdr pattern)) #f)))) ; Match with the pattern but no problem if it does not match. (define (match-opt input pattern) (let ((match (match-pattern input (car pattern)))) (if match match input))) ; Match anything (other than '()), until pattern is found. The rather ; clumsy form of requiring an ending pattern is needed to decide where ; the end of the match is. If none is given, this will match the rest ; of the sentence. (define (match-any input pattern) (cond ((null? (remain input)) #f) ((null? pattern) (f-cons (remain input) (clear-remain input))) (else (let ((accum-any (collector))) (define (match-pattern-any input pattern) (cond ((null? (remain input)) #f) (else (accum-any (car (remain input))) (cond ((match-pattern (r-cdr input) pattern)) (else (match-pattern-any (r-cdr input) pattern)))))) (let ((retval (match-pattern-any input (car pattern)))) (if retval (f-cons (accum-any) retval) #f)))))) MIME types defined: text/x-scheme.
