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|
(load "load")
;;; Problem 5.2 and 5.3
; I redefined match:element to take an optional additional parameter
; ugly style here, haha!
(define (match:element variable . predicate)
(let ((pred (if (eq? (length predicate) 1)
(environment-lookup (nearest-repl/environment) (car predicate))
(lambda (q) #t))))
(define (element-match data dictionary succeed)
(and (pair? data)
(let ((vcell (match:lookup variable dictionary)))
(if vcell
(and (equal? (match:value vcell) (car data))
(succeed dictionary 1))
(if (pred (car data))
(succeed (match:bind variable (car data) dictionary)
1)
#f)))))
element-match))
(define (match:variable-predicate pattern)
(caddr pattern))
(defhandler match:->combinators
(lambda (pattern) (if (eq? (length pattern) 3)
(match:element (match:variable-name pattern)
(match:variable-predicate pattern))
(match:element (match:variable-name pattern))))
match:element?)
(define (matcher pattern)
(let ((match-combinator (match:->combinators pattern)))
(lambda (datum)
(match-combinator
(list datum)
'()
(lambda (dictionary number-of-items-eaten)
(and (= number-of-items-eaten 1)
dictionary))))))
#| Test it!
((matcher '(a (?? t) c))
'(a 4 4 4 4 4 c))
;Value: ((t (4 4 4 4 4)))
((matcher '(a (? b integer?) c))
'(a 4 c))
;Value: ((b 4))
((matcher '(a (? b integer?) c))
'(a thing c))
; #f
((matcher '(a (? b integer? 4) (? b integer?) c))
'(a 3 3 c))
; ((b c))
; hmmmm.... i'm just going to call this user error
((matcher '(a (? b) (? b integer?) c))
'(a t t c))
; ((b t))
|#
;;; Problem 5.4
(define (match:choice? pattern)
(and (pair? pattern)
(eq? (car pattern) '?:choice)))
(define (match:choice match-choices)
(define (choice-match data dictionary succeed)
(let lp ((m-c match-choices))
(if (pair? m-c)
(let ((try ((match:->combinators (car m-c))
data
dictionary
succeed)))
(if try
try
(lp (cdr m-c))))
#f)))
choice-match)
(defhandler match:->combinators
(lambda (x) (match:choice (cdr x)))
match:choice?)
#| TEST TIME!
((matcher '(a (?:choice 2 4 6 8) c))
'(a 8 c))
; ()
((matcher '((?? b) 4 (?:choice (? a) (? b) 'other) 8))
'(t t t t t t 4 t 8))
;Value: ((a t) (b (t t t t t t)))
((matcher '((?? b) 4 (?:choice (? b) other) 8))
'(t t t t t t 4 other 8))
;Value: ((b (t t t t t t)))
|#
;;; Problem 5.5
(define *pattern-table* '())
(define (pattern-lookup name)
(let lp ((table *pattern-table*))
(cond ((null? table) #f)
((eq? name (caar table))
(begin
(display "FOUND!")
(car (cdr (car table)))))
(else (lp (cdr table))))))
(define (matcher pattern)
(let ((match-combinator (match:->combinators pattern)))
(lambda (datum)
(set! *pattern-table* '())
(match-combinator
(list datum)
'()
(lambda (dictionary number-of-items-eaten)
(and (= number-of-items-eaten 1)
dictionary))))))
(define (match:pletrec? pattern)
(and (pair? pattern)
(eq? (length pattern) 2)
(eq? (car pattern) '?:pletrec)))
(define (match:pletrec bindings body)
(display "made a letrec")
(define (pletrec-match data dictionary succeed)
(display "trying a letrec")
(for-each
(set! *pattern-table* (cons (list (car x) (cadr x))
*pattern-table*))
bindings)
((match:->combinator body)
data
dictionary
succeed))
pletrec-match)
(defhandler match:->combinators
(lambda (bindings body)
(display bindings)
(display body)
(match:pletrec bindings body))
match:pletrec?)
(define (match:ref? pattern)
(and (pair? pattern)
(eq? (car pattern) '?:ref)))
(define (match:ref name)
(let ((pattern (pattern-lookup name)))
(define (ref-match data dictionary succeed)
((match:->combinator pattern)
data
dictionary
succeed))
ref-match))
(defhandler match:->combinators
match:ref
match:ref?)
(define (match:list? pattern)
(and (list? pattern)
(not (memq (car pattern) '(? ?? ?:ref ?:pletrec ?:choice)))))
#| Test Round, GO!
(match:pletrec? '(?:pletrec ((odd (?:choice () (1 ?:ref even)))
(even (?:choice () (2 ?:ref odd))))))
; #t
(match:list? '(?:pletrec ((odd (?:choice () (1 ?:ref even)))
(even (?:choice () (2 ?:ref odd))))))
; #f
((match:->combinators '(?:pletrec ((odd (?:choice () (1 ?:ref even)))
(even (?:choice () (2 ?:ref odd))))
(?:ref odd)))
'(a b c)
'()
(lambda
((matcher '(?:pletrec ((fancy (1 2 3)))
(?:ref fancy)))
'(1 2 3 4 6 7 ))
((matcher '(?:pletrec ((odd (?:choice () (1 ?:ref even)))
(even (?:choice () (2 ?:ref odd))))
(?:ref odd)))
'(1 (2 (1 ()))))
*pattern-table*
|#
|
