EoPL reading (66) 2.2 An Abstraction for Inductive Data Type
うーん、迷走気味。現時点にて parse な試験で問題発生中。
test unparse (4), expects (lambda (x) (f x y)) ==> ERROR: GOT #<error "wrong number of arguments for #<closure (unparse-expression unparse-expression)> (required 2, got 3)"> test unparse (5), expects (lambda (x) (x)) ==> ERROR: GOT #<error "wrong number of arguments for #<closure (unparse-expression unparse-expression)> (required 2, got 1)">
実装を控え。まず、expression.scm から
(add-load-path ".")
(load "define-datatype")
(define list-of
(lambda (pred)
(lambda (val)
(or (null? val)
(and (pair? val)
(pred (car val))
((list-of pred) (cdr val)))))))
(define-datatype expression expression?
(lit-exp
(datum number?))
(var-exp
(id symbol?))
(if-exp
(test-exp expression?)
(true-exp expression?)
(false-exp expression?))
(lambda-exp
(ids (list-of symbol?))
(body expression?))
(app-exp
(rator expression?)
(rands (list-of expression?))))次は parse.scm
(add-load-path ".")
(load "define-datatype")
(define unparse-expression
(lambda (exp)
(cases expression exp
(lit-exp (datum) datum)
(var-exp (id) id)
(if-exp (test-exp true-exp false-exp)
(list 'if test-exp true-exp false-exp))
(lambda-exp (ids body)
(list 'lambda ids
(unparse-expression body)))
(app-exp (rator rands)
(list (unparse-expression rator)
(unparse-expression rands))
))))
(define parse-expression
(lambda (datum)
(cond
((number? datum) (lit-exp datum))
((symbol? datum) (var-exp datum))
((pair? datum)
(cond ((eqv? (car datum) 'lambda)
(lambda-exp (cadr datum)
(parse-expression (caddr datum))))
((eqv? (car datum) 'if)
(if-exp (cadr datum) (caddr datum) (cadddr datum)))
(else
(let f ((rslt '(app-exp)) (datum datum))
(if (null? datum)
rslt
(f (append rslt (list (parse-expression (car datum))))
(cdr datum)))))))
(else
(eopl:error 'parse-expression
"Invalid concrete symtax ~s" datum)))))あと、parse の試験も以下に。
(use gauche.test)
(add-load-path ".")
(load "define-datatype")
(load "expression")
(load "occurs-free")
(load "parse")
(test-start "parse")
(test-section "unparse-expression")
(test* "unparse (1)"
'a
(unparse-expression '(var-exp a)))
(test* "unparse (2)"
'(lambda (x) x)
(unparse-expression '(lambda-exp (x) (var-exp x))))
(test* "unparse (3)"
'((lambda (x) x) a)
(unparse-expression '(app-exp (lambda-exp (x) (var-exp x)) (var-exp a))))
(test* "unparse (4)"
'(lambda (x) (f x y))
(unparse-expression '(lambda-exp (x) (app-exp (var-exp f) (var-exp x) (var-exp y)))))
(test* "unparse (5)"
'(lambda (x) (x))
(unparse-expression '(lambda-exp (x) (app-exp (var-exp x)))))
(test* "unparse (6)"
'(lambda (x y z) x)
(unparse-expression '(lambda-exp (x y z) (var-exp x))))
(test* "unparse (7)"
'(lambda () x)
(unparse-expression '(lambda-exp () (var-exp x))))
(test-section "parse-expression")
(test* "parse (1)"
'(var-exp a)
(parse-expression 'a))
(test* "parse (2)"
'(lambda-exp (x) (var-exp x))
(parse-expression '(lambda (x) x)))
(test* "parse (3)"
'(app-exp (lambda-exp (x) (var-exp x)) (var-exp a))
(parse-expression '((lambda (x) x) a)))
(test* "parse (4)"
'(lit-exp 5)
(parse-expression 5))
(test* "parse (5)"
*test-error*
(parse-expression "a"))
(test* "parse (6)"
'(app-exp (var-exp a) (var-exp b) (var-exp c))
(parse-expression '(a b c)))
(test* "parse (7)"
'(app-exp (lambda-exp (x) (app-exp (var-exp +) (var-exp x) (var-exp x))) (var-exp a))
(parse-expression '((lambda (x) (+ x x)) a)))
(test* "parse (8)"
'(lambda-exp (x) (app-exp (var-exp x)))
(parse-expression '(lambda (x) (x))))
(test-end)なんとなく見えてるのは
- (app-exp (var-exp f) (var-exp x) (var-exp y)) は引数 3 つなので引数二つな app-exp の呼び出しに対応不可能
- (app-exp (var-exp x)) は引数 1 つなので (ry
という事。だったら app-exp な分岐を以下にしたらどうか、とトライしてみると
discrepancies found. Errors are: test unparse (1): expects a => got #<error "proper list required, but got (rator . rands)"> test unparse (2): expects (lambda (x) x) => got #<error "proper list required, but got (rator . rands)"> test unparse (3): expects ((lambda (x) x) a) => got #<error "proper list required, but got (rator . rands)"> test unparse (4): expects (lambda (x) (f x y)) => got #<error "proper list required, but got (rator . rands)"> test unparse (5): expects (lambda (x) (x)) => got #<error "proper list required, but got (rator . rands)"> test unparse (6): expects (lambda (x y z) x) => got #<error "proper list required, but got (rator . rands)"> test unparse (7): expects (lambda () x) => got #<error "proper list required, but got (rator . rands)">
って叱られる。可変長引数にマッチ可能な syntax-rules の書き方がどうか、が分かれば問題解決なのでしょうか。色々試験してみているんですが、途中中断
ってか今日はこのまま終了。
追記
昨晩、エントリ投入途上で寝落ちしてました。ちなみに盛り込んだ実装は以下になります。
(app-exp (rator rands) ;; (list (unparse-expression rator) ;; (unparse-expression rands)) (append (list (unparse-expression rator)) (if (pair? rands) (unparse-expression rands) (if (null? rands) '() (list rands)))))
解決の糸口が全く見えてません。いったん最初から見直した方が良さげ。
