modulus operator "%" versus fmod

[exquisitus]

I'm trying to decide which of these two to use to calculate the
remainder between two floating point numbers. My gut instinct says to go
for the % operator - but I'm not sure if I am right. Which is the
correct one (i.e. more effecient) and why?

Thanks

[Michael Mair]

exquisitus wrote:

I'm trying to decide which of these two to use to calculate the
remainder between two floating point numbers. My gut instinct says to go
for the % operator - but I'm not sure if I am right. Which is the
correct one (i.e. more effecient) and why?

The % operator only works for integer arguments; moreover, as
% is defined in terms of / (i.e. a -(a/b)*b == a%b, if b!=0),
there is no sensible value, as we do not necessarily "lose"
something (which also could be recovered by a % operation)
by a "floating point" division.

So, fmod() is your way to go.
Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.

[exquisitus]

Michael Mair wrote:

exquisitus wrote:

I'm trying to decide which of these two to use to calculate the
remainder between two floating point numbers. My gut instinct says to
go for the % operator - but I'm not sure if I am right. Which is the
correct one (i.e. more effecient) and why?

The % operator only works for integer arguments; moreover, as
% is defined in terms of / (i.e. a -(a/b)*b == a%b, if b!=0),
there is no sensible value, as we do not necessarily "lose"
something (which also could be recovered by a % operation)
by a "floating point" division.

So, fmod() is your way to go.
Cheers
Michael

Thanks Michael !

[Joe Wright]

exquisitus wrote:

I'm trying to decide which of these two to use to calculate the
remainder between two floating point numbers. My gut instinct says to go
for the % operator - but I'm not sure if I am right. Which is the
correct one (i.e. more effecient) and why?

Thanks

Gut instinct can give you a tummy ache. You should be looking for
correctness, not efficiency. Better to read something. Do you have a C
book? "The % operator cannot be applied to float or double." is quite
prominent in my book.

--
Joe Wright mailto:jo********@comcast.net
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---