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brag/parser-tools/private-lex/util.rkt

128 lines
3.7 KiB
Racket

#lang racket/base
(require (for-syntax racket/base))
(provide (all-defined-out))
(define max-char-num #x10FFFF)
(define-struct lex-abbrev (get-abbrev))
(define-struct lex-trans (f))
(module+ test
(require rackunit))
(define-syntax (test-block stx)
(syntax-case stx ()
[(_ defs (code right-ans) ...)
#'(module+ test
(require rackunit)
(let* defs
(let ([real-ans code])
(check-equal? real-ans right-ans)) ...))]))
#;(define-syntax test-block
(syntax-rules ()
((_ x ...) (void))))
;; A cache is (X ( -> Y) -> Y)
;; make-cache : -> cache
;; table map Xs to Ys. If key is mapped, its value is returned.
;; Otherwise, build is invoked and its result is placed in the table and
;; returned.
;; Xs are compared with equal?
(define (make-cache)
(let ([table (make-hash)])
(λ (key build)
(hash-ref table key (λ ()
(let ([new (build)])
(hash-set! table key new)
new))))))
(module+ test
(define cache (make-cache))
(check-equal? (cache '(s 1 2) (λ () 9)) 9)
(check-equal? (cache '(s 2 1) (λ () 8)) 8)
(check-equal? (cache '(s 1 2) (λ () 1)) 9)
(check-equal? (cache (cons 's (cons 0 (cons +inf.0 10)))
(λ () 22)) 22)
(check-equal? (cache (cons 's (cons 0 (cons +inf.0 10)))
(λ () 1)) 22))
;; make-counter : -> -> nat
;; makes a function that returns a higher number by 1, each time
;; it is called.
(define (make-counter)
(let ([counter 0])
(λ ()
(begin0
counter
(set! counter (add1 counter))))))
(module+ test
(define c (make-counter))
(define d (make-counter))
(check-equal? (c) 0)
(check-equal? (d) 0)
(check-equal? (c) 1)
(check-equal? (d) 1)
(check-equal? (c) 2))
;; remove-dups : (list-of X) (X -> number) -> (list-of X)
;; removes the entries from l that have the same index as a
;; previous entry. l must be grouped by indexes.
(define (remove-dups l index acc)
(cond
[(null? l) (reverse acc)]
[(null? acc) (remove-dups (cdr l) index (cons (car l) acc))]
[(= (index (car acc)) (index (car l)))
(remove-dups (cdr l) index acc)]
[else
(remove-dups (cdr l) index (cons (car l) acc))]))
(module+ test
(check-equal? (remove-dups '((1 2) (2 2) (1 3) (1 4)
(100 4) (0 5)) cadr null)
'((1 2) (1 3) (1 4) (0 5)))
(check-equal? (remove-dups null error null) null))
;; do-simple-equiv : (list-of X) (X -> nat) -> (list-of X)
;; Sorts l according to index and removes the entries with duplicate
;; indexes.
(define (do-simple-equiv l index)
(define ordered (sort l (λ (a b) (< (index a) (index b)))))
(remove-dups ordered index null))
(module+ test
(check-equal? (do-simple-equiv '((2 2) (1 4) (1 2)
(100 4) (1 3) (0 5))
cadr)
'((2 2) (1 3) (1 4) (0 5)))
(check-equal? (do-simple-equiv null error) null))
;; replace : (list-of X) (X -> bool) (X -> (list-of X)) (list-of X) ->
;; (list-of X)
;; If (pred? r) for some r in l, splice (get r) in place of r in the resulting
;; list.
(define (replace l pred? get acc)
(cond
[(null? l) acc]
[(pred? (car l)) (replace (cdr l) pred? get (append (get (car l)) acc))]
[else (replace (cdr l) pred? get (cons (car l) acc))]))
(module+ test
(check-equal? (replace null void (λ () (list 1)) null) null)
(check-equal? (replace '(1 2 3 4 3 5)
(λ (x) (= x 3))
(λ (x) (list 1 2 3))
null)
'(5 1 2 3 4 1 2 3 2 1)))