Load the exponent of a radix-independent floating point number
#include <math.h> double scalbn ( double x, int n ); float scalbnf ( float x, int n ); long double scalbnl ( long double x, int n );
The scalbn(), scalbnf(), and scalbnl() functions compute x × r^{n}, where r is the radix of the machine's floating-point arithmetic. The difference between the scalbn* and scalbln* functions is the type of the second argument.
To check for error situations, use feclearexcept() and fetestexcept():
x × r^{n}
If a range error due to overflow occurs, a range error occurs, and these functions return ±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL, as appropriate. If a range error due to underflow occurs, the correct result (after rounding) is returned.
#include <stdio.h> #include <inttypes.h> #include <math.h> #include <fenv.h> #include <stdlib.h> int main( void ) { double a, b, c, d; int except_flags; feclearexcept(FE_ALL_EXCEPT); a = 10; b = 2; c = scalbn(a, b); except_flags = fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW); if(except_flags) { /* An error occurred; handle it appropriately. */ } feclearexcept(FE_ALL_EXCEPT); d = sqrt(c/a); except_flags = fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW); if(except_flags) { /* An error occurred; handle it appropriately. */ } printf("Radix of machine's fp arithmetic is %f \n", d); printf("So %f = %f * (%f ^ %f) \n", c, a, d, b); return EXIT_SUCCESS; }
produces the output:
Radix of machine's fp arithmetic is 2.000000 So 40.000000 = 10.000000 * (2.000000 ^ 2.000000)
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | No |
Thread | Yes |