25dd8727cb
This library is used by Redex, which wants a `syntax'-like template language, but for datum values instead of syntax objects. Using `datum-case' and `datum' generates much less code. Redex uses only a small part of the general functionality, so adding `syntax/datum' could be overkill. It's implemented by generalizing the `syntax-case' and `syntax' pattern matching and template constructing code, though; it's not a lot of extra code, and it's easiest to generalize completely. We may find other uses for datum templates, too.
58 lines
1.4 KiB
Racket
58 lines
1.4 KiB
Racket
#lang racket
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(require syntax/datum)
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(define (do-test expect got expr)
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(unless (equal? expect got) (error "failed\n" expr)))
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(define-syntax test
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(syntax-rules (datum-case datum)
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[(_ expect (datum-case expr () [pat (datum tmpl)]))
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(begin
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(test expect (values (datum-case expr () [pat (datum tmpl)])))
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(test expect (with-datum ([pat expr]) (datum tmpl))))]
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[(_ expect expr)
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(do-test expect expr 'expr)]))
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(test '(3 2 1)
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(datum-case '(1 2 3) ()
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[(a b c) (datum (c b a))]))
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(test '(3 1 2)
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(datum-case '(1 2 3) ()
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[(a ... c) (datum (c a ...))]))
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(test '(3 1 2)
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(datum-case '#(1 2 3) ()
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[#(a ... c) (datum (c a ...))]))
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(test '(3 2 1)
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(datum-case '#(1 2 3) ()
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[#(a b c) (datum (c b a))]))
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(test '(3 2 1)
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(datum-case '#s(q 1 2 3) ()
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[#s(q a b c) (datum (c b a))]))
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(test '(3 2 1)
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(datum-case '(1 ! 2 % 3) (! %)
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[(a ! b % c) (datum (c b a))]))
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(test '(3 2 1)
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(datum-case '#(1 ! 2 % 3) (! %)
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[#(a ! b % c) (datum (c b a))]))
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(test 'x
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(datum x))
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(test 'x
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(quasidatum x))
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(test '(1 2 3)
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(quasidatum (1 (undatum (+ 1 1)) 3)))
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(test '#(1 2 3)
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(quasidatum #(1 (undatum (+ 1 1)) 3)))
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(test '(1 2 3)
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(quasidatum (1 (undatum-splicing (list (+ 1 1) 3)))))
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(test '(1 2 3 4)
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(quasidatum (1 (undatum-splicing (list (+ 1 1) 3)) 4)))
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