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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); double expm1 (dou- ble x); float expm1f (float x); double log (double x); float logf (float x); double log2 (double x); float log2f (float x); double log10 (double x); float log10f (float x); double log1p (double y); float log1pf (float y); double pow (double x, double y); float powf (float x, float y); STANDARDS Interfaces documented on this reference page conform to industry stan- dards 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 in- dustry standards and associated tags. DESCRIPTION The exp() and expf() 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() and expm1f() functions compute exp(x) - 1 accurately, even for tiny x. The log() and logf() functions compute the natural (base e) logarithm of x. The log2() and log2f() functions compute the base 2 logarithm of x. The log10() and log10f() functions compute the common (base 10) loga- rithm of x. The log1p() and log1pf() functions compute log(1+y) accurately, even for tiny y. The pow() and powf() 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 refer- ence 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 excep- tional arguments: tab(@); lfHB lfHB lfHB l l l . _ Function@Exceptional Argument@Routine Behavior _ exp(), expf()@x > ln(max_float)@Overflow exp(), expf()@x < ln(min_float)@Underflow expm1(), expm1f()@x > ln(max_float)@Overflow expm1(), expm1f()@x < ln(min_float)@Underflow log(), logf()@x < 0@Invalid argument log(), logf()@x = 0@Overflow log2(), log2f()@x < 0@Invalid argument log2(), logf2()@x = 0@Overflow log10(), log10f()@x < 0@Invalid argument log10(), log10f()@x = 0@Overflow log1p(), log1pf()@1+y < 0@Invalid argument log1p(), log1pf()@1+y = 0@Overflow pow(), powf()@y ln(x) > ln(max_float)@Overflow pow(), powf()@y ln(x) < ln(min_float)@Underflow _ The following table lists boundary values used by these functions: tab(@); lfHB lfHB lfHB lfHB lfHB lfHB lfHB lfHB l l l l . _ 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)