Re: Predicate for a string representing an integer

[Jan-Peter Voigt]

Hi Urs,

the functions used are built-in so I'd probably also do it (almost) that 
way. But I'd strongly recommend to test if obj is a string first:

#(define (integer-string? obj)
   (and (string? obj)(integer? (string->number obj))))

Otherwise the predicate fails with an error (not false) if the argument 
is something else ... for example an integer.
I doubt that checking all characters in the string are in the range 
'0'-'9' is faster then string->number.

Jan-Peter

Am 30.05.2017 um 10:47 schrieb Urs Liska:
> Hi all,
>
> I've found this function in my code:
>
> % Returns true if obj is a string representation of an integer
> #(define (integer-string? obj)
>     (integer? (string->number obj)))
>
> and I have the impression there should be a better way with more
> built-in functionality to do it.
>
> Any suggestions, or should I simply leave it at that?
>
> Urs