Hi -
On 5/21/15, 7:42 AM, "Damian McGuckin" <[email protected]> wrote:
>
>Why would a 32 bit floating point number multiplied by a 32 bit integer
>yield a 64 bit quantity? Is Chapel trying to avoid overflow?
Yes. This behavior matches the language specification.
In section 9.1.1, it says that int(32) won't coerce to real(32)
since a real(32) can't represent an int(32) without loss of precision.
Note though that int(64) can coerce to real(64) as "an important
convenience."
Then, in section 10.13.5, the spec says that * is only defined for the
same type.
Function resolution could not find *(real(32), int(32)), but it
did find *(real(64), real(64)) since real(32) can coerce to real(64)
and int(32) can coerce to real(64).
Modifying your program like this provides the behavior you expected:
var x : real(32) = 0.5:real(32);
var i : int(32) = 12345;
var m = x * (i:real(32));
if m.type == real(64) then
{
writeln("64 bits was seen");
}
else
{
writeln("I expect 32 bits");
}
I'd be interested to know your thoughts on this property - do
you think that int(32) should coerce to real(32)?
Cheers,
-michael
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