• #ponce (5/5) Mar 22 2010 I never knew exactly what the float-to-int C cast is supposed to do.
• Trass3r (2/6) Mar 22 2010 I've never heard anything else but truncate. Rounding can thus be done
• Lionello Lunesu (2/12) Mar 22 2010 or -0.5f when f < 0.0
• Jesse Phillips (3/8) Mar 22 2010 I've never considered anything but truncate.
• #ponce (2/6) Mar 23 2010 Well, ok it's not. It's just that it seems to me that it's useless and c...
• Jonathan M Davis (8/16) Mar 23 2010 Maybe I've just never talked to enough programmers about it, but I've ne...

#ponce <ponce.remove-me adinpsz.org> writes:

I never knew exactly what the float-to-int C cast is supposed to do. 

float f = whatever();
int b = cast(int) f;


Does it truncate, floor or round ? Or even undefined, depending on the rounding
mode ? I just asked to 3 fellow programmers, it seems like i'm not the onlyone
to find this confusing.

Why should a destructive cast should be _that_ implicit anyway ?

Trass3r <un known.com> writes:

 I never knew exactly what the float-to-int C cast is supposed to do.

 float f = whatever();
 int b = cast(int) f;


 Does it truncate, floor or round ?

I've never heard anything else but truncate. Rounding can thus be done  
with cast(int)(f + 0.5f).

Lionello Lunesu <lio lunesu.remove.com> writes:

On 23-3-2010 7:59, Trass3r wrote:
 I never knew exactly what the float-to-int C cast is supposed to do.

 float f = whatever();
 int b = cast(int) f;


 Does it truncate, floor or round ?

 
 I've never heard anything else but truncate. Rounding can thus be done
 with cast(int)(f + 0.5f).

or -0.5f when f < 0.0

Jesse Phillips <jessekphillips+D gmail.com> writes:

#ponce wrote:

 I never knew exactly what the float-to-int C cast is supposed to do. 

 float f = whatever();
 int b = cast(int) f;


 Does it truncate, floor or round ? Or even undefined, depending on the
rounding mode ? I just asked to 3 fellow programmers, it seems like i'm not the
onlyone to find this confusing.

 Why should a destructive cast should be _that_ implicit anyway ?

I've never considered anything but truncate.

Also how is it implicit?

#ponce <ponce.SPAMM adinpsz.org> writes:

 
 I've never considered anything but truncate.
 
 Also how is it implicit?

Well, ok it's not. It's just that it seems to me that it's useless and
confusing.
If it's really trunc, I have seen countless errors where it was used as floor.

Jonathan M Davis <jmdavisProg gmail.com> writes:

#ponce wrote:

 
 I've never considered anything but truncate.
 
 Also how is it implicit?

 
 Well, ok it's not. It's just that it seems to me that it's useless and
 confusing. If it's really trunc, I have seen countless errors where it was
 used as floor.

Maybe I've just never talked to enough programmers about it, but I've never 
talked to one who thought that it was anything other than truncate. I would 
have expected it to be mentioned in a decent C or C++ primer, but I haven't 
read any in a while, so I don't recally whether it's typical for it to be 
mentioned there. However, it is quite standard for C-derived languages to 
truncate when casting from float to integer.

- Jonathan M Davis