C99 complex support with visual studio
No matter what you do, you can't make "float complex" parse properly in a non-C99 compiler. So instead of writing that, make some typedefs. It's far easier if you only have to support one complex type, so I'll just demonstrate with float complex
.
First, define the types:
#if __STDC_VERSION__ >= 199901L
//using a C99 compiler
#include <complex.h>
typedef float _Complex float_complex;
#else
typedef struct
{
float re, im;
} float_complex;
#endif
Then, we need to be able to create complex numbers, and emulate creal and cimag.
#if __STDC_VERSION__ >= 199901L
//creal, cimag already defined in complex.h
inline complex_float make_complex_float(float real, float imag)
{
return real + imag * I;
}
#else
#define creal(z) ((z).re)
#define cimag(z) ((z).im)
extern const complex_float complex_i; //put in a translation unit somewhere
#define I complex_i
inline complex_float make_complex_float(float real, float imag)
{
complex_float z = {real, imag};
return z;
}
#endif
Next, write functions that wrap addition, subtraction, multiplication, division, and comparisons.
#if __STDC_VERSION__ >= 199901L
#define add_complex(a, b) ((a)+(b))
//similarly for other operations
#else //not C99
inline float_complex add_complex(float_complex a, float_complex b)
{
float_complex z = {a.re + b.re, a.im + b.im};
return z;
}
//similarly for subtract, multiply, divide, and comparison operations.
Note that add_complex(c, 5)
doesn't work in C89 mode in the above code, because the compiler doesn't know how to make 5 into a complex. This is a tricky problem to fix in C without compiler support -- you have to resort to tricks like the new tgmath.h
uses, which are compiler-specific.
Unfortunately, the effect of all of this is that the nice C99 syntax like a+b
to add complex numbers has to be written add_complex(a, b)
.
Another option (as another poster pointed to) is to use C++ std::complex
on non-C99 compilers. This might be OK if you can wrap things in typedefs and #ifdef
s. However, you'd require either C++ or C99.