I am new to scheme. This is code sample from SICP course of MIT.
(define (+ x y)
(if (= x 0)
y
(+ (-1+ x) (1+ y))))
How do I convert this to Racket code? I want to convert to Racket because I am using DrRacket for running codes and I like that. It worked until now but complained about increment operators of scheme.
The errors I get are:
define-values: cannot change constant variable: +reference to undefined identifier: -1+This will work fine in Racket:
(define (add x y)
(if (= x 0)
y
(add (sub1 x) (add1 y))))
Some comments:
+ for the procedure will be troublesome, because it will clash with the primitive add operation in Scheme; it's simpler if you use a different name, like add (this will fix the first error)-1+ is not a procedure in Racket, replace it with sub1 (this will fix the second error). Optionally, you could define an alias for this procedure, like this: (define -1+ sub1)1+ is not a procedure in Racket, replace it with add1. Optionally, you could define an alias for this procedure, like this: (define 1+ add1)(= x 0) you can write (zero? x)To fix the second error, change (-1+ x) to (- x 1) and (1+ y) to (+ y 1). This answer should help you with the first error.
If you want to use -1+ and 1+, you can define them yourself:
(define (1+ x) (+ x 1))
(define (-1+ x) (- x 1))
#langbased language (e.g.,#lang racket), you can redefine primitives like+that are from the language. If you are using a student language, it will restrict you in order to provide better error reporting. - Asumu Takikawa#lang schemeis an old backwards compatibility language. You probably want to just use#lang racket. I bet you're getting this error due to setting your memory limit too low or your program has a bug (e.g., infinite loop). - Asumu Takikawa