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How to use a "long int" in GNU Prolog?

So basically it seems that GNU Prolog use 28bit integer on my 32bit x86 Linux.

The code below can not be compiled:

foo(A) :-
   A0 is 0xdeadbeef,
   A1 is A0 >> 8,
   A2 is A0 >> 16,
   A3 is A0 >> 24.

Then I am confused with two typical situations below:

  1. How to represent a 32bit integer in GNU Prolog (like 0xdeadbeef)? and pushing it further, how to represent a 64 bit integer ? On 64 bit x86 Linux, long long type in C has 64 bit.

  2. When using GNU Prolog to call C, the interface defined in the manual has integer, positive and others.. then if I want to pass a 32bit integer from Prolog to C, which type should I choose..? I found an ad-hoc solution and writing it in this question, is there any better solution?

Could anyone give me some help?

Solution

  • GNU Prolog uses bounded integers, whose bounds depend on the architecture (32/64 bits). You can know these limits with (on a 64 bits):

    | ?- current_prolog_flag(min_integer,X).

X = -1152921504606846976

yes
| ?- current_prolog_flag(max_integer,X).

X = 1152921504606846975

    yes

    A workaround to store bigger integers is to spit them into 2 parts and for instance use a Prolog structure to record them.