<math.h> problem

[John B.]

I'm self teaching myself C on a Linux box but I can't get a simple program
to recognize math functions. I start the program with:

#include <stdio.h>
#include <math.h> but when I compile the program, it does not
recognize sin(x); or pow(x,y) etc, in any equation.

/usr/include does have a math.h file. Any help or things to try would
be greatly appreciated!!!!. (I do alot of graphic things with trig.)
thanks j1**@yahoo.com

[Ben Pfaff]

"John B." <j1**@yahoo.com> writes:

I'm self teaching myself C on a Linux box but I can't get a simple program
to recognize math functions. I start the program with:

You forgot to read the FAQ.
--
"I am worth much more brick-bat!!"
--Uday Joshi

[Tim Hagan]

"John B." wrote:

I'm self teaching myself C on a Linux box but I can't get a simple program
to recognize math functions. I start the program with:

#include <stdio.h>
#include <math.h> but when I compile the program, it does not
recognize sin(x); or pow(x,y) etc, in any equation.

/usr/include does have a math.h file. Any help or things to try would
be greatly appreciated!!!!. (I do alot of graphic things with trig.)
thanks j1**@yahoo.com

It's a FAQ.

14.3: I'm trying to do some simple trig, and I am #including <math.h>,
but I keep getting "undefined: sin" compilation errors.

A: Make sure you're actually linking with the math library. For
instance, under Unix, you usually need to use the -lm option, at
the *end* of the command line, when compiling/linking. See also
questions 13.25, 13.26, and 14.2.

See the rest at http://www.eskimo.com/~scs/C-faq/top.html

--
Tim Hagan

[Derk Gwen]

"John B." <j1**@yahoo.com> wrote:
# I'm self teaching myself C on a Linux box but I can't get a simple program
# to recognize math functions. I start the program with:
#
# #include <stdio.h>
# #include <math.h> but when I compile the program, it does not
# recognize sin(x); or pow(x,y) etc, in any equation.

It compiles but has link errors? On most platform, you have to link the math
library. On unices this is done with a -lm on the ld command (or *cc command
used to call ld).

--
Derk Gwen http://derkgwen.250free.com/html/index.html
GERBILS
GERBILS
GERBILS

[Kevin Bracey]

In message <vj************@corp.supernews.com>
Derk Gwen <de******@HotPOP.com> wrote:

"John B." <j1**@yahoo.com> wrote:
# I'm self teaching myself C on a Linux box but I can't get a simple
# program to recognize math functions. I start the program with:

It compiles but has link errors? On most platform, you have to link the
math library. On unices this is done with a -lm on the ld command (or *cc
command used to call ld).

I've never quite understood why this is. Presumably it has something to
do with reducing code size, but are Unix linkers not sophisticated enough to
omit unused portions of libraries automatically?

Surely a modern Unix C environment could default to including the whole ISO C
library and omit the portions not required?

--
Kevin Bracey, Principal Software Engineer
Tematic Ltd Tel: [phone]
182-190 Newmarket Road Fax: [phone]
Cambridge, CB5 8HE, United Kingdom WWW: http://www.tematic.com/