ldexp(3) [osf1 man page]
frexp(3) Library Functions Manual frexp(3) NAME
frexp, ldexp, logb, scalb - Manipulate floating-point numbers LIBRARY
Math Library (libm.a) SYNOPSIS
#include <math.h> double frexp (double x, int *n); float frexpf (float x, int *n); long double frexpl (long double x, int *n); double ldexp (double y, int n); float ldexpf (float y, int n); long double ldexpl (long double y, int n); double logb (double x); float logbf (float x); long double logbl (long double x); double scalb (double x, double n); float scalbf (float x, float n); long double scalbl (long dou- ble x, long double n); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: frexp(): XPG4 ldexp(): XPG4 logb(): XPG4-UNIX scalb(): XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. DESCRIPTION
Every nonzero number can be written uniquely as the normalized mantissa (fraction) z times 2 raised to the power p, where the absolute value of z is in the range [0.5, 1.0), and the exponent p, is an integer. The frexp(), frexpf(), and frexpl() functions break a floating-point number into a normalized fraction and an integral power of 2. The functions store the integer in the int object pointed to by the n parameter and return the fraction part. The ldexp(), ldexpf(), and ldexpl() functions multiply a floating-point number, y, by an integral power of 2. The logb(), logbf(), and logbl() functions return a signed integer converted to double-precision floating-point and so chosen that 1 <= |x|/2**n < 2 unless x = 0 or |x| = infinity or x lies between 0 and the Underflow Threshold. IEEE 754 defines logb(+infinity) = +infinity and logb(0) = -infinity. The latter is required to signal Division-by-Zero. The scalb(), scalbf(), and scalbl() functions are defined as x*(2**n) for integer n. The following table describes function behavior in response to exceptional arguments: ---------------------------------------------------------------------- Function Exceptional Argument Routine Behavior ---------------------------------------------------------------------- frexp(), frexpf(), frexpl() |x| = infinity Invalid argument logb(), logbf(), logbl() |x| = infinity Invalid argument scalb(), scalbf(), scalbl() x*(2**n) > max_float Overflow scalb(), scalbf(), scalbl() x*(2**n) < min_float Underflow ldexp(), ldexpf(), ldexpl() x*(2**n) > max_float Overflow ldexp(), ldexpf(), ldexpl() x*(2**n) < min_float Underflow ---------------------------------------------------------------------- The following table lists boundary values used by these functions: -------------------------------------------------------------------- Value Name Data Type Hexadecimal Value Decimal Value -------------------------------------------------------------------- max_float S_FLOAT 7F7FFFFF 3.402823e38 T_FLOAT 7FEFFFFFFFFFFFFF 1.797693134862316e308 min_float S_FLOAT 00000001 1.4012985e-45 T_FLOAT 0000000000000001 4.940656458412465e-324 -------------------------------------------------------------------- delim off frexp(3)
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exp(3) Library Functions Manual exp(3) NAME
exp, expm1, log, log2, log10, log1p, pow - Exponential, logarithm, and power functions LIBRARY
Math Library (libm.a) SYNOPSIS
#include <math.h> double exp (double x); float expf (float x); long double expl (long double x); double expm1 (double x); float expm1f (float x); long double expm1l (long double x); double log (double x); float logf (float x); long double logl (long double x); double log2 (double x); float log2f (float x); long double log2l (long double x); double log10 (double x); float log10f (float x); long double log10l (long double x); double log1p (double y); float log1pf (float y); long double log1pl (long double y); double pow (double x, double y); float powf (float x, float y); long double powl (long double x, long double y); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: exp(): XPG4 expm1(): XPG4-UNIX log(): XPG4 log10(): XPG4 log1p(): XPG4-UNIX pow(): XPG4 Refer to the standards(5) reference page for more information about industry standards and associated tags. DESCRIPTION
The exp(), expf(), and expl() functions compute the value of the exponential function, defined as e**x, where e is the constant used as a base for natural logarithms. The expm1(), expm1f(), and expm1l() functions compute exp(x) - 1 accurately, even for tiny x. The log(), logf(), and logl() functions compute the natural (base e) logarithm of x. The log2(), log2f(), and log2l() functions compute the base 2 logarithm of x. The log10(), log10f(), and log10l() functions compute the common (base 10) logarithm of x. The log1p(), log1pf(), and log1pl() functions compute log(1+y) accurately, even for tiny y. The pow(), powf(), and powl() functions raise a floating-point base x to a floating-point exponent y. The value of pow(x,y) is computed as e**(y ln(x)) for positive x. If x is 0 or negative, see your language reference manual. Passing a NaN input value to pow() produces a NaN result for y not equal to 0. For pow(NaN,0), see your language reference manual. The following table describes function behavior in response to exceptional arguments: ------------------------------------------------------------------------- Function Exceptional Argument Routine Behavior ------------------------------------------------------------------------- exp(), expf(), expl() x > ln(max_float) Overflow exp(), expf(), expl() x < ln(min_float) Underflow expm1(), expm1f(), expm1l() x > ln(max_float) Overflow expm1(), expm1f(), expm1l() x < ln(min_float) Underflow log(), logf(), logl() x < 0 Invalid argument log(), logf(), logl() x = 0 Overflow log2(), log2f(), log2l() x < 0 Invalid argument log2(), logf2(), log2l() x = 0 Overflow log10(), log10f(), log10l() x < 0 Invalid argument log10(), log10f(), log10l() x = 0 Overflow log1p(), log1pf(), log1pl() 1+y < 0 Invalid argument log1p(), log1pf(), log1pl() 1+y = 0 Overflow pow(), powf(), powl() y ln(x) > ln(max_float) Overflow pow(), powf(), powl() y ln(x) < ln(min_float) Underflow ------------------------------------------------------------------------- The following table lists boundary values used by these functions: ----------------------------------------------------------------------------- Value Data Hexadecimal Value Decimal Value Name Type ----------------------------------------------------------------------------- ln(max_float) S_FLOAT 42B17218 88.7228391 T_FLOAT 40862E42FEFA39EF 709.7827128933840 ln(min_float) S_FLOAT C2CE8ED0 -103.2789 T_FLOAT C0874385446D71C3 -744.4400719213813 ----------------------------------------------------------------------------- delim off exp(3)