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Question about the failure of "abs" to compute the complex value's magnitude

Yu Zhang39
Intellectual 510 points

Hello:

 

   I am trying to manipulate the complex values in CCSv5 and run in C6713 dsk.

 

 

   What confused me was that I added header file "complex.h" and called the function creal and cimag.  Both of them worked.
   But if i want to call abs to determine the magnitude of the complex number, it did not work properly.  It should incorrect values instead.

 

   Snapshot:

 

 

 

You see, the first and second was correct but the third one, it was supposed to be "5.0" but why it showed -1.0?

 

I really don't know why this weird problem happend? Is abs obsolete or changed according to the update of the lib?

 

Thank you

 

Yu

 

 

  • 0
    Expert 1810 points
    In C, abs() takes an "int" argument. cabs() takes a "double complex" argument. If type-generic math is available and enabled (by #include <tgmath.h>), then fabs() will take any floating-point scalar or complex argument, and expand to the "right" variant of the fabs[fl]() or cabs[fl]() functions. Does using cabs() make the final printout show 5.0?