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frexp

Break down x into a mantissa (a floating point with an absolute value between [1/2, 1)) and an integral exponent for 2, and return the mantissa. The exponent is stored in the position pointed by exp.

Interface Definition

C interface:

float frexpf(float x, int *exp);

double frexp(double x, int *exp);

long double frexpl(long double x, int *exp);

Parameters

Parameter

Type

Description

Input/Output

x
  • For frexpf, x is of single-precision floating-point type.
  • For frexp, x is of double-precision floating-point type.
  • For frexpl, x is of long double-precision floating-point type.

Floating-point value of the input data.

Input

exp

An integer pointer.

Exponent.

Output

Return Value

  • x is broken down into a mantissa (a floating point with an absolute value between [1/2, 1)) and an integral exponent for 2, and the mantissa is returned. The exponent is stored in the position pointed by exp.
  • If input x is inf, the return value is inf, and the return value of exp is meaningless.
  • If input x is -inf, the return value is -inf, and the return value of exp is meaningless.
  • If input x is NaN, the return value is NaN, and the return value of exp is meaningless.

Dependency

C: "km.h"

Example

C interface:
    // print result
    int32_t exp;
    printf("frexp(3.4, &exp) = %.15f, exp = %d\n", frexp(3.4, &exp), exp);
    printf("frexp(-4.8, &exp) = %.15f, exp = %d\n", frexp(-4.8, &exp), exp);
    printf("frexp(NAN, &exp) = %.15f, exp = %d\n", frexp(NAN, &exp), exp);
    printf("frexp(-NAN, &exp) = %.15f, exp = %d\n", frexp(-NAN, &exp), exp);
    printf("frexp(INFINITY, &exp) = %.15f, exp = %d\n", frexp(INFINITY, &exp), exp);
    printf("frexp(-INFINITY, &exp) = %.15f, exp = %d\n", frexp(-INFINITY, &exp), exp);

result
    /* 
     * frexp(3.4, &exp) = 0.850000000000000, exp = 2
     * frexp(-4.8, &exp) = -0.600000000000000, exp = 3
     * frexp(NAN, &exp) = nan, exp = 3
     * frexp(-NAN, &exp) = -nan, exp = 3
     * frexp(INFINITY, &exp) = inf, exp = 3
     * frexp(-INFINITY, &exp) = -inf, exp = 3
     * */