Question

Use DrRacket to write a Scheme program that takes a list and computes the number of atoms in the list. Name your source code num_atoms.rkt. Here are some examples > (num atoms '((a b) c (d (e f)))) 6 > (num_ atoms '(1 2 34 5)) >(num_atoms '((1 2 3 45))) >(num atoms (O))

Answer 1

Code:

(define (num_atoms lst)

(cond ((null? lst) 0) ;;empty list returns 0

((list? (car lst)) (+ (num_atoms (car lst)) (num_atoms (cdr lst)))) ;;First element of list is itself a list count number of elements in it and add it to length of the rest of list

(else (+ 1 (num_atoms (cdr lst)))))) ;;else count it and recursivrly count rest of the elements

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Snapshots of Code and Output:

1 (define (num atoms 1st) (cond ((null? 1st) 0) ;;empty list returns θ ((list? (car 1st)) (num_atoms (car 1st)) (num atoms (cdr 1st))First element of list is itself a list count number of elements in it and add it to length of the rest of list (else ( 1 (num atoms (cdr 1st)))))) jelse count it and recursivrly count rest of the element 4

Biwascheme Interpreter version 0.6.4 Copyright (C) 2007-2014 Yutaka HARA and the BiwaScheme team (num_atoms ((a b) c (d (e f))) (num_atoms (1 2 345)) (num_atoms ((1 2 345))) (num_atoms(O)) =〉 6 => 5