Originální popis anglicky:
exp2, exp2f, exp2l - exponential base 2 functions
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double exp2(double
x);
float exp2f(float
x);
long double exp2l(long double
x);
These functions shall compute the base-2 exponential of
x.
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.
Upon successful completion, these functions shall return 2
**x.
If the correct value would cause overflow, a range error shall occur and
exp2(),
exp2f(), and
exp2l() shall return the value of
the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If the correct value would cause underflow, and is not representable, a range
error may occur, and either 0.0 (if supported), or an
implementation-defined value shall be returned.
If
x is NaN, a NaN shall be returned.
If
x is ±0, 1 shall be returned.
If
x is -Inf, +0 shall be returned.
If
x is +Inf,
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.
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.
The following sections are informative.
None.
For IEEE Std 754-1985
double, 1024 <=
x implies
exp2(
x) has overflowed. The value
x < -1022
implies
exp(
x) has underflowed.
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but at
least one of them must be non-zero.
None.
None.
exp() ,
feclearexcept() ,
fetestexcept() ,
isnan() ,
log() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
Conditions for Mathematical Functions,
<math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
