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 16 · Answer 1 · answered Jul 21 '11 at 20:20

16

Use atom_number/2. E.g:

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

answered Jul 21 '11 at 20:20

gusbro

22,357
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1

Strictly, that's an atom, not a string. – Fred Foo Jul 21 '11 at 20:26

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

355,277
75
744
836

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

20,356
6
40
33

score 2 · Answer 4 · answered Oct 17 '20 at 22:07

2

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

Docs

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

For those who are still looking for it.

answered Oct 17 '20 at 22:07

Omar

105
1
3
12

Karman · Answer 5 · 2023-02-04T18:53:01.783

0

A simple example using Visual Prolog 10
==============================
% UNS-EPISI-LAB-IA

implement main
    open core

clauses
    run() :-
        console::write("Valor de A? "),
        A = console::readLine(),
        console::write("Valor de B? "),
        B = console::readLine(),
        Areal = toTerm(real, A),
        Breal = toTerm(real, B),
        console::write("A + B = ", Areal + Breal),
        _ = console::readChar().

end implement main

goal
    console::runUtf8(main::run).

edited Feb 04 '23 at 18:53

answered Dec 08 '22 at 15:53

Karman

1
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Welcome to SO! Good solution, but I think it isn't quite relevant, because OP explicitly asked for SWI-Prolog solution. – hurufu Dec 13 '22 at 16:04

score -1 · Answer 6 · 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

99
4

Prolog: how to convert string to integer?

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