cabs, cabsl

Remonter à Math.h - Index

Header File

math.h

Category

Math Routines

Prototype

double cabs(struct complex z);

long double cabsl(struct _complexl z);

Description

cabs calculates the absolute value of a complex number. cabs is a macro that calculates the absolute value of z, a complex number. z is a structure with type complex; the structure is defined in math.h as

struct complex {

double x, y;

};

where x is the real part, and y is the imaginary part.

Calling cabs is equivalent to calling sqrt with the real and imaginary components of z, as shown here:

sqrt(z.x * z.x + z.y * z.y)

cabsl is the long double version; it takes a structure with type _complexl as an argument, and returns a long double result. The structure is defined in math.h as

struct _complexl {

long double x, y;

};

Return Value

cabs (or cabsl) returns the absolute value of z, a double. On overflow, cabs (or cabsl) returns HUGE_VAL (or _LHUGE_VAL) and sets the global variable errno to

ERANGE

Result out of range

Error handling for these functions can be modified through the functions _matherr and _matherrl.

Example

 #include <stdio.h>
 #include <math.h>
 #ifdef __cplusplus
   #include <complex.h>
 #endif
 #ifdef __cplusplus /* if C++, use class complex */
   void print_abs(void)
   {
     complex<float> z(1.0, 2.0);
     double  absval;
     absval = abs(z);
     printf("The absolute value of %.2lfi %.2lfj is %.2lf",
       real(z), imag(z), absval);
   }
 #else  /* below function is for C (and not C++) */
   void print_abs(void)
   {
     struct complex z;
     double absval;
     z.x = 2.0;
     z.y = 1.0;
     absval = cabs(z);
     printf("The absolute value of %.2lfi %.2lfj is %.2lf",
       z.x, z.y, absval);
   }
 #endif
 int main(void)
 {
   print_abs();
   return 0;
 }

Portability

	POSIX	Win32	ANSI C	ANSI C++
cabs		+
cabsl		+