%---------------------------------------------------------------------------%
% vim: ts=4 sw=4 et ft=mercury
%---------------------------------------------------------------------------%
%
% A very basic check of arithmetic on big integers.

:- module integer_test.
:- interface.
:- import_module io.

:- pred main(io__state, io__state).
:- mode main(di, uo) is det.

:- implementation.
:- import_module int.
:- import_module integer.
:- import_module list.
:- import_module require.
:- import_module string.

main -->
    { X = integer.det_from_string("+1234567890987654321") },
    { Y = integer.det_from_string(
        "98765432101234567890123400000009999111") },
    { Z = integer(200) },
    test(X, Y, Z).

:- pred test(integer, integer, integer, io__state, io__state).
:- mode test(in, in, in, di, uo) is det.

test(X, Y, Z) -->
    {
        Plus = X + Y,
        Times = X * Y,
        Minus = X - Y,
        Div = Y // X,
        Rem = Y rem X,
        Pow = integer.pow(X, Z),
        fac(Z, Fac)
    },
    write_message("X: ", X),
    write_message("Y: ", Y),
    write_message("Z: ", Z),
    write_message("X + Y: ", Plus),
    write_message("X * Y: ", Times),
    write_message("X - Y: ", Minus),
    write_message("Y // X: ", Div),
    write_message("Y rem X: ", Rem),
    write_message("fac(Z): ", Fac),
    write_message("pow(X,Z): ", Pow),
    { X0 = integer(100000), X1 = integer(3) },
    write_integer(X0), io.write_string(" div mod "),
        write_integer(X1), io.write_string(" = "),
        write_integer(X0 div X1), io.write_string(" "),
        write_integer(X0 mod X1), io.nl,
    write_integer(-X0), io.write_string(" div mod "),
        write_integer(X1), io.write_string(" = "),
        write_integer(X0 div -X1), io.write_string(" "),
        write_integer(X0 mod -X1), io.nl,
    write_integer(X0), io.write_string(" div mod "),
        write_integer(-X1), io.write_string(" = "),
        write_integer(-X0 div X1), io.write_string(" "),
        write_integer(-X0 mod X1), io.nl,
    write_integer(-X0), io.write_string(" div mod "),
        write_integer(-X1), io.write_string(" = "),
        write_integer(-X0 div -X1), io.write_string(" "),
        write_integer(-X0 mod -X1), io.nl,
    write_integer(X0), io.write_string(" // rem "),
        write_integer(X1), io.write_string(" = "),
        write_integer(X0 // X1), io.write_string(" "),
        write_integer(X0 rem X1), io.nl,
    write_integer(-X0), io.write_string(" // rem "),
        write_integer(X1), io.write_string(" = "),
        write_integer(X0 // -X1), io.write_string(" "),
        write_integer(X0 rem -X1), io.nl,
    write_integer(X0), io.write_string(" // rem "),
        write_integer(-X1), io.write_string(" = "),
        write_integer(-X0 // X1), io.write_string(" "),
        write_integer(-X0 rem X1), io.nl,
    write_integer(-X0), io.write_string(" // rem "),
        write_integer(-X1), io.write_string(" = "),
        write_integer(-X0 // -X1), io.write_string(" "),
        write_integer(-X0 rem -X1), io.nl,
    { int.min_int(Minint) },
        ( { integer(Minint) < integer(0) } ->
            io.write_string("integer(min_int) ok\n")
        ;
            io.write_string("integer(min_int) failed\n")
        ).

:- pred write_message(string, integer, io__state, io__state).
:- mode write_message(in, in, di, uo) is det.

write_message(String, Int) -->
    io__write_string(String),
    { Str = integer.to_string(Int) },
    io__write_string(Str),
    io__nl.

:- pred fac(integer, integer).
:- mode fac(in, out) is det.

fac(X, F) :-
    ( X =< integer.zero ->
        F = integer.one
    ;
        fac(X - integer.one, F1),
        F = F1 * X
    ).

:- pred write_integer(integer, io.state, io.state).
:- mode write_integer(in, di, uo) is det.
write_integer(X) -->
    { S = integer.to_string(X) },
    io.write_string(S).