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scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl: vypočítat exponent pomocí FLT_RADIX

Originální popis anglicky: scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl - compute exponent using FLT_RADIX

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

#include <math.h>
 
 
double scalbln(double x, long n );
 
float scalblnf(float x, long n);
 
long double scalblnl(long double x, long n );
 
double scalbn(double x, int n);
 
float scalbnf(float x, int n);
 
long double scalbnl(long double x, int n );
 

POPIS / INSTRUKCE

These functions shall compute x * FLT_RADIX**n efficiently, not normally by computing FLT_RADIX **n explicitly.
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.

NÁVRATOVÁ HODNOTA

Upon successful completion, these functions shall return x * FLT_RADIX **n.
If the result would cause overflow, a range error shall occur and these functions shall return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x) as appropriate for the return type of the function.
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 or ±Inf, x shall be returned.
If n 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.

CHYBY / ERRORY

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.

PŘÍKLADY POUŽITÍ

None.

APPLICATION USAGE

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.

RATIONALE

These functions are named so as to avoid conflicting with the historical definition of the scalb() function from the Single UNIX Specification. The difference is that the scalb() function has a second argument of double instead of int. The scalb() function is not part of the ISO C standard. The three functions whose second type is long are provided because the factor required to scale from the smallest positive floating-point value to the largest finite one, on many implementations, is too large to represent in the minimum-width int format.

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

feclearexcept() , fetestexcept() , scalb() , 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 .
2003 IEEE/The Open Group
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