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Has anyone got any idea what the idiomatic method for nested looping on numbers within a range is in Racket/Scheme? In Python we have:
for i in range(numb1):
for j in range(numb2):
What would be the equivalent in Racket/Scheme?
245
In Racket it's as simple as this, using Iterations and Comprehensions:
(for* ([i (in-range numb1)]
[j (in-range numb2)])
<body of iteration>)
The above will only work in Racket. By comparison, the following snippets will work in any standard RxRS interpreter - for instance, using a pair of nested do:
(do ((i 0 (+ i 1))) ((= i numb1))
(do ((j 0 (+ j 1))) ((= j numb2))
<body of iteration>))
Yet another option: using explicit recursion and named let:
(let loop1 ((i 0))
(cond ((< i numb1)
(let loop2 ((j 0))
(cond ((< j numb2)
<body of iteration>
(loop2 (+ j 1)))))
(loop1 (+ i 1)))))
Finally, you can always do something like the following, refer to SICP under the section "Nested Mappings" for details:
(define (range start stop)
(let loop ((i (- stop 1))
(acc '()))
(if (< i start)
acc
(loop (- i 1) (cons i acc)))))
(for-each
(lambda (i)
(for-each
(lambda (j)
<body of iteration>)
(range 0 numb2)))
(range 0 numb1))
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