TSS depth*

listのネストの深さを調べる手続きdepth*。

取り合えず書いてみた。いまいち。

	; depth*
	; (define max (with-module gauche max))
	(define (depth* l)
	(if (null? l)
	1
	(let ((kar (car l))
	(d (depth* (cdr l))))
	(if (list? kar)
	(max (+ 1 (depth* kar))
	d)
	d))))
	; fold
	(define (depth* l)
	(fold (lambda (e acc)
	(max (if (list? e)
	(+ 1 (depth* e))
	acc)
	acc))
	1 l))
	(depth* '((pickled) peppers (peppers pickled)))
	; -> 2
	(depth* '())
	; -> 1
	(depth* '(()
	((bitter butter)
	(makes)
	(batter
	(bitter)))
	butter))
	; -> 4

view raw 14.LetThereBeNames.scm hosted with ❤ by GitHub

The Seasoned Schemer. chapter 14.

	; The Seasoned Schemer
	(define add1
	(lambda (n)
	(+ n 1)))
	(define depth*
	(lambda (l)
	(cond
	((null? l) 1)
	((atom? (car l))
	(depth* (cdr l)))
	(else
	(cond
	((> (depth* (cdr l))
	(add1 (depth* (car l))))
	(depth* (cdr l)))
	(else
	(add1 (depth* (car l)))))))))
	(depth* '((pickled) peppers (peppers pickled)))
	; -> 2
	(depth* '())
	; -> 1
	(depth* '(()
	((bitter butter)
	(makes)
	(batter
	(bitter)))
	butter))
	; -> 4
	; The Seasoned Schemer letting
	(define depth*
	(lambda (l)
	(cond
	((null? l) 1)
	((atom? (car l))
	(depth* (cdr l)))
	(else
	(let ((a (add1 (depth* (car l))))
	(d (depth* (cdr l))))
	(cond
	((> d a) d)
	(else a)))))))
	(depth* '((pickled) peppers (peppers pickled)))
	; -> 2
	(depth* '())
	; -> 1
	(depth* '(()
	((bitter butter)
	(makes)
	(batter
	(bitter)))
	butter))
	; -> 4
	; The Seasoned Schemer, if
	(define max
	(lambda (n m)
	(if (> n m) n m)))
	(define depth*
	(lambda (l)
	(cond
	((null? l) 1)
	((atom? (car l))
	(depth* (cdr l)))
	(else (max
	(add1 (depth* (car l)))
	(depth* (cdr l)))))))
	(depth* '((pickled) peppers (peppers pickled)))
	; -> 2
	(depth* '())
	; -> 1
	(depth* '(()
	((bitter butter)
	(makes)
	(batter
	(bitter)))
	butter))
	; -> 4

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