2016-02-22 22:46 GMT+01:00 Federico Ramírez <[email protected]>:
(define (tokenize input)
> (cond
> ((match-identifier input) (consume-identifier input))
> ((match-equals input) (consume-equals input))
> ((match-number input) (consume-number input))
> (else '())))
>
> What bothers me is that it's calling the matchers twice for each token,
> which isn't very good for performance and it's not pretty :p
>
You can use this strategy:
(define (tokenize input)
(cond
((match-identifier input) => (lambda (token) ... consume the
identifier token...))
((match-equals input) => (lambda (token) ... consume the
equals token...))
((match-number input) => (lambda (token) ... consume the number
token...))
(else '())))
Here a clause of the form [expression1 => expression2] will calls the
result of expression2
with the result of expression1 as input. That is: when (match-identifier
input) returns a token
the function (lambda (token) ... consume the identifier token...) will be
called with the token.
Given the token you can find it's length n and then skip n bytes of the
input stream.
--
Jens Axel Søgaard
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