======P9.5.scm====== <code shell>#!/usr/bin/env racket #lang racket/base</code> věci kolem deep, stromů, linearizace, hloubková rekurze na seznamech viz Lekce 9, [[P9.scm]] ======= linearize ======= <hidden linearizace vnořených seznamů, rekurze> <code scheme> (define (linearize l) (cond ((null? l) '()) ((list? (car l)) (append (linearize (car l)) (linearize (cdr l)))) (else (cons (car l) (linearize (cdr l)))))) </code> dtto:(append (list (car l)) (linearize ...)) </hidden> <code scheme> (linearize '((1 2 3) (4 5 6) (7 (8)) 9)) </code> ======= atoms ======= <hidden počet atomů ve vnořených seznamech, rekurze> <code scheme> (define (atoms l) (cond ((null? l) 0) ((list? (car l)) (+ (atoms (car l)) (atoms (cdr l)))) (else (+ 1 (atoms (cdr l)))))) </code> </hidden> <code scheme> (atoms '((1 2 3) (4 5 6) (7 (8)) 9)) </code> [[#linearize]] [[#atoms]] jsou si podobné, => [[#deep-accum]] <hidden hloubková akumulační procedura> <code scheme> (define (deep-accum combine nula modif l) (cond ((null? l) nula) ((list? (car l)) (combine (deep-accum combine nula modif (car l)) (deep-accum combine nula modif (cdr l)))) (else (combine (modif (car l)) (deep-accum combine nula modif (cdr l)))))) </code> </hidden> <code scheme> (define deep9 '((1 2 3) (4 5 6) (7 (8)) 9 (1 (1 1) 2 3))) (deep-accum + 0 (lambda (x) 1) '((1 2 3) (4 5 6) (7 (8)) 9)) (deep-accum append '() list '((1 2 3) (4 5 6) (7 (8)) 9)) </code> <hidden počet atomů určité hodnoty> <code scheme> (define (deep-count atom l) (deep-accum + 0 (lambda (x) (if (equal? atom x) 1 0)) l)) </code> </hidden> <code scheme> (deep-count 1 deep9) (deep-count 2 deep9) </code> <hidden přítomnost atomu ve strultuře> <code scheme> (define (deep-find atom l) (deep-accum (lambda (x y) (or x y)) ;combine #f (lambda (x) (equal? atom x)) ;modif l)) </code> </hidden> <code scheme> (deep-find 1 deep9) (deep-find 22 deep9) </code> <hidden hloubkové nahrazování> <code scheme> (define (deep-replace p? modif l) (deep-accum cons '() (lambda (x) (if (p? x) (modif x) x)) l)) </code> </hidden> <code scheme> (deep-replace even? - deep9) </code> <hidden linearize pomocí apply, append map> <code scheme> (define (linearize2 l) (if (list? l) (apply append (map linearize2 l)) (list l);hotovo, prazdny nebo atom )) </code> </hidden> <code scheme> (linearize2 deep9) </code> <hidden atoms2 pomocí apply, append map> <code scheme> (define (atoms2 l) (if (list? l) (apply + (map atoms2 l)) 1;hotovo, prazdny nebo atom )) </code> </hidden> <code scheme> (atoms2 '()) (atoms2 deep9) </code> => deep-accum2, ta ma 2. nedostatky monoidalní operace -> arbitrary, <code scheme> (define (arbitrary mono-op nil) (lambda args (foldr mono-op nil args)));vyšší řád, vrací proceduru! (define cons/n (arbitrary cons '())) (cons/n 1 2 3 4 5 6) </code> todo <code scheme> (define (deep-replace2 p? modif l) l) ; vim: syntax=racket </code>