simplify loop

master
Matthew Butterick 4 years ago
parent 059196c48f
commit 140d537c4b

@ -1,5 +1,5 @@
#lang br
(require racket/file rackunit racket/set)
(require racket/file rackunit racket/set racket/dict)
(define (line->wire ln)
;; convert string to a wire
@ -10,21 +10,17 @@
(define (wire->locs wire)
;; list of every grid location visited by a wire
(for/fold ([locs (list 0)]
#:result (reverse locs))
([move (in-list wire)])
(append
(match move
[(cons dir dist)
(define origin (car locs))
(for/fold ([locs null])
([i (in-range dist)])
(define next-loc (+ origin (* (match dir
['L -1]
['R 1]
['U +i]
['D -i]) (add1 i))))
(cons next-loc locs))]) locs)))
;; use complex numbers to model x, y locations
(for*/fold ([locs (list 0)]
#:result (reverse locs))
([(dir dist) (in-dict wire)]
[complex-unit (in-value (match dir
['L -1]
['R 1]
['U +i]
['D -i]))]
[i (in-range dist)])
(cons (+ (car locs) complex-unit) locs)))
(define test-w1 (line->wire "R8,U5,L5,D3"))
(check-equal?