Prolog: how to convert string to integer?

Question

So as the title says - how do you convert a string into an integer? the idea is something like this:

convert(String,Integer).

examples:
convert('1',1).
convert('33',33).

I'm using swi prolog

possible duplicate of [Parsing numbers with multiple digits in Prolog](http://stackoverflow.com/questions/3279822/parsing-numbers-with-multiple-digits-in-prolog) — Ted Hopp, Jul 21 '11 at 20:05
@Ted Hopp: not a dupe, the other question has the specific context of DCGs. This can be done more easily. The OP has to decide whether a string or an atom is given, though. — Fred Foo, Jul 21 '11 at 20:24

score 15 · Answer 1 · answered Jul 21 '11 at 20:20

15

Use atom_number/2. E.g:

  atom_number('123', X).
  X = 123.

answered Jul 21 '11 at 20:20

gusbro

score 12 · Answer 2 · answered Jul 21 '11 at 20:25

12

Assuming you really meant a string and not an atom, use number_codes.

?- number_codes(11, "11").
true.

?- number_codes(11, Str).
Str = [49, 49].            % ASCII/UTF-8

?- number_codes(N, "11").
N = 11.

answered Jul 21 '11 at 20:25

Fred Foo

score 5 · Answer 3 · answered Jul 21 '11 at 20:10

5

Perhaps use of atom_codes(?Atom, ?String) and number_chars(?Number, ?CharList) would do it.

answered Jul 21 '11 at 20:10

MRAB

score 0 · Answer 4 · answered Oct 17 '20 at 22:07

0

Quite an old, but there is a predicate in SWI Prolog: number_string(N, S).

number_string(123, S).
S = "123".

For those who are still looking for it.

answered Oct 17 '20 at 22:07

Omar

score -1 · Answer 5 · answered Dec 21 '17 at 11:33

-1

in Visual Prolog convert:

X=toTerm(real,H).

real/integer/unsigned...

answered Dec 21 '17 at 11:33

Drovosek

5 Answers5