:- module main.
:- interface.
:- import_module io.
:- pred main(io::di, io::uo) is det.
:- implementation.
:- import_module string, int.
:- pred add(int::in, int::in, int::out) is det.
:- pragma foreign_proc("C",
add(A::in, B::in, Result::out),
[will_not_call_mercury, promise_pure, thread_safe],
"
int add(int a, int b) {
return a + b;
}
Result = add(A,B);
").
main(!IO) :-
io.read_line_as_string(ResultA, !IO),
(
ResultA = ok(LineA),
StrippedA = string.strip(LineA),
( if string.to_int(StrippedA, A) then
io.read_line_as_string(ResultB, !IO),
(
ResultB = ok(LineB),
StrippedB = string.strip(LineB),
( if string.to_int(StrippedB, B) then
add(A, B, Sum),
io.write_string("The sum is: ", !IO),
io.write_int(Sum, !IO),
io.nl(!IO)
else
B = 0,
add(A, B, Sum),
io.write_string("The sum is: ", !IO),
io.write_int(Sum, !IO),
io.nl(!IO)
)
;
ResultB = eof,
io.write_string("Unexpected end of second input\n", !IO)
;
ResultB = error(ErrorCode),
io.write_string(io.error_message(ErrorCode) ++ "\n", !IO)
)
else
A = 0,
B = 0,
add(A, B, Sum),
io.write_string("The sum is: ", !IO),
io.write_int(Sum, !IO),
io.nl(!IO)
)
;
ResultA = eof,
io.write_string("Unexpected end of first input\n", !IO)
;
ResultA = error(ErrorCode),
io.write_string(io.error_message(ErrorCode) ++ "\n", !IO)
).
