Increment and Decrement operators in scheme programming language
They are not defined as such since Scheme and Racket try to avoid mutation; but you can easily define them yourself:
(define-syntax incf (syntax-rules () ((_ x) (begin (set! x (+ x 1)) x)) ((_ x n) (begin (set! x (+ x n)) x)))) (define-syntax decf (syntax-rules () ((_ x) (incf x -1)) ((_ x n) (incf x (- n)))))
> (define v 0) > (incf v) 1 > v 1 > (decf v 2) -1 > v -1
Note that these are syntactic extensions (a.k.a. macros) rather than plain procedures because Scheme does not pass parameters by reference.
-> (add1 3) 4 -> (sub1 3) 2
The operators 1+ and -1+ do /not/ mutate, as a simple experiment in MIT Scheme will show:
1 ]=> (define a 3) ;Value: a 1 ]=> (1+ a) ;Value: 4 1 ]=> (-1+ a) ;Value: 2 1 ]=> a ;Value: 3
So you can implement your own function or syntactic extensions of those functions by having them evaluate to (+ arg 1) and (- arg 1) respectively.
unknownerror 3 months
What are the
schemeprogramming language. I am using "Dr.Racket" and it is not accepting
1+as operators. And, I have also tried
decf, but no use.
unknownerror over 5 yearsThis will not change that value of variable you are passing. Have a look here: ideone.com/KEgO9g