phoenix-rtos-doc / libc / functions / l / ldexp.part-impl.md

ldexp

Synopsis

#include <math.h>

double ldexp(double x, int exp);

float ldexpf(float x, int exp);

long double ldexpl(long double x, int exp);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

These functions shall compute the quantity x * 2^exp.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Return value

Upon successful completion, these functions shall return x multiplied by 2, raised to the power exp.

If these functions caused overflow, a range error shall occur and ldexp(), ldexpf(), and ldexpl() shall return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x), respectively.

If the correct value would cause underflow, and is not representable, a range error may occur, and ldexp(), ldexpf(), and ldexpl() shall return 0.0, or (if IEC 60559 Floating-Point is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

If x is NaN, a NaN shall be returned.
If x is ±0 or ±Inf, x shall be returned.
If exp is 0, x shall be returned.
If the correct value would cause underflow, and is representable, a range error may occur, and the correct value shall be returned.

Errors

These functions shall fail if:

Range Error - The result overflows. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to ERANGE. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

These functions may fail if:

Range Error - The result underflows. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to ERANGE. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

Tests

Untested

Known bugs

None