function
<cmath> <ctgmath>
ldexp
double ldexp (double x, int exp);
double ldexp (double x , int exp); float ldexpf (float x , int exp);long double ldexpl (long double x, int exp);
double ldexp (double x , int exp); float ldexp (float x , int exp);long double ldexp (long double x, int exp);
double ldexp (double x , int exp); float ldexp (float x , int exp);long double ldexp (long double x, int exp); double ldexp (T x , int exp); // additional overloads for integral types
Generate value from significand and exponent
Returns the result of multiplying x (the significand) by 2 raised to the power of exp (the exponent).
lexpr(x,exp) = x * 2 exp
Header
<tgmath.h> provides a type-generic macro version of this function.
Additional overloads are provided in this header (
<cmath>) for the
integral types: These overloads effectively cast
x to a
double before calculations (defined for
T being any
integral type).
Parameters
- x
- Floating point value representing the significand.
- exp
- Value of the exponent.
Return Value
The function returns:
x * 2 exp
If the magnitude of the result is too large to be represented by a value of the return type, the function returns HUGE_VAL (or HUGE_VALF or HUGE_VALL) with the proper sign, and an overflow range error occurs:
If an overflow
range error occurs, the global variable
errno is set to
ERANGE.
Example
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/* ldexp example */
#include <stdio.h> /* printf */
#include <math.h> /* ldexp */
int main ()
{
double param, result;
int n;
param = 0.95;
n = 4;
result = ldexp (param , n);
printf ("%f * 2^%d = %f\n", param, n, result);
return 0;
}
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Output:
0.950000 * 2^4 = 15.200000
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See also
- frexp
- Get significand and exponent (function)
- log
- Compute natural logarithm (function)
- pow
- Raise to power (function)