Thread: Trying to create an exp(x) program

Once you take out the erroneous double in "b = double exp(x);" everything looks like it should work.

I had tried that and I get a crazy error:

Code:

Undefined                       first referenced
 symbol                             in file
exp                                 /var/tmp//ccsUdNwM.o
ld: fatal: Symbol referencing errors. No output written to a.out
collect2: ld returned 1 exit status

And of course, somewhere along the way you should remember that to include the math library using gcc you need to add "-lm" to the end of your compilation line.

Forgot about that. But now there's a new problem. The program just returns exactly what I input. I.e. after it asks for a number, I input 6 and it returns the number 6.

Ok I figured it out:

Code:

#include <stdio.h>
#include <math.h>

main()
{
        double x;
        double b;

        printf("Enter an exponent for base e\n");
        scanf("%lf", &x);

        b = exp(x);
        printf("exp(%f) is equivalent to %lf\n", x, b);
}

But one last thing. The final printf (example) reads something like

Code:

exp(2.000000) is equivalent to 7.389056

Is there a way to make it so that the program doesn't spit out so many decimal places? I.e. can it just say 2.00 instead of 2.0000000...?

printf uses %f for doubles.

you can use the field width thing:

%1.2f

Thanks!

what do you mean by add -lm to to the end of the compilation line

so would it be like

gcc-lm <filename>