Re: How to use trigonometric functions in Swarm?

[Paul E. Johnson]

Perrone Alessandro wrote:
> 
> I imported the right header, but when I call the sin(x) function, an
> error occur!!
> I am using Linux on my Imac, with Swarm 2.1.1
> Here it is the result with a simple program:
> 
> ------
> address@hidden apps]# gcc alex.c -o alex
> /tmp/ccHDfVDm.o: In function `main':
> /tmp/ccHDfVDm.o(.text+0x20): undefined reference to `sin'
> /tmp/ccHDfVDm.o(.text+0x20): relocation truncated to fit: R_PPC_REL24 sin
> collect2: ld returned 1 exit status
> address@hidden apps]# more alex.c
> #include <stdio.h>
> #include <math.h>
> 
> int main () {
>     float a;
>     a=(float) sin((double) 1.0);
>     printf("%f\n",a);
> return 0;
> }
> address@hidden apps]# gcc -I/usr/include alex.c -o alex

I use the math library in RedHat linux by including the math.h as you
do, and it works fine, when I compile a Swarm program.  I was reading
the C faq last week (http://www.faqs.org/faqs/C-faq/faq/) and this math
question is in there.  Gary's point about -lm is correct.  Swarm does it
automatically, without any intervention from me. The "-lm" line appears
in the output of the linker, I mean to say.

But I have one thing to add, which is that I think that the sin function
is expecting to have a value for PI*X in the parentheses if you want
sin(x), and the values you want are in math.h. M_PIl is a long double
value on this system. Like this:
     valueSinX = sin(M_PIl*X);

-- 
Paul E. Johnson                         email: address@hidden
Dept. of Political Science              http://lark.cc.ukans.edu/~pauljohn
University of Kansas                    Office: (785) 864-9086
Lawrence, Kansas 66045                  FAX: (785) 864-5700

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