NAME

exp, log, log10, pow, sqrt − exponential, logarithm, power, square root functions

NOTICE

This entry is not identical to the corresponding entry in the HP-UX Reference.  It was modified after the manual went to print to conform to the XPG3 Standard.  Change bars in the right-hand margin show additions and changes.  An asterisk in the right margin indicates deleted text. 

SYNOPSIS

#include <math.h>

double exp (x)
double x;

double log (x)
double x;

double log10 (x)
double x;

double pow (x, y)
double x, y;

double sqrt (x)
double x;

DESCRIPTION

Exp returns ex. 

Log returns the natural logarithm of x. The value of x must be positive. 

Log10 returns the logarithm base ten of x. The value of x must be positive. 

Pow returns xy.  If x is 0.0, y must be positive.  If x is negative, y must be an integer. 

Sqrt returns the non-negative square root of x. The value of x must not be negative. 

DEPENDENCIES

Series 300
The algorithms used are those from HP 9000 BASIC. 

Series 800 (/lib/libm.a)
Exp returns:

• +INFINITY when x is +INFINITY ,

• 0.0 when x is −INFINITY . 

Log and log10 return +INFINITY when x is +INFINITY . 

Pow returns +INFINITY when:

• Absolute value of x is greater than 1.0 and y is +INFINITY ,

• Absolute value of x is less than 1.0 and y is −INFINITY ,

• x is +INFINITY and y is greater than 0.0, or

• x is −INFINITY and y is an even integer. 

Pow returns −INFINITY when x is −INFINITY and y is an odd integer. 

Pow returns 0.0 when:

• Absolute value of x is greater than 1.0 and y is −INFINITY ,

• absolute value of x is less than 1.0 and y is +INFINITY ,

• x is +INFINITY and y is less than 0.0. 

Sqrt returns +INFINITY when x is +INFINITY . 

Series 800 (ANSI C /lib/libM.a)
Exp returns:

• +INFINITY when x is +INFINITY ,

• 0.0 when x is −INFINITY . 

Log and log10 return +INFINITY when x is +INFINITY . 

Pow returns 1.0 when x and y are both 0.0. 

Pow returns +INFINITY when:

• Absolute value of x is greater than 1.0 and y is +INFINITY ,

• Absolute value of x is less than 1.0 and y is −INFINITY ,

• x is +INFINITY and y is greater than 0.0, or

• x is −INFINITY and y is an even integer. 

Pow returns −INFINITY when x is −INFINITY and y is an odd integer. 

Pow returns 0.0 when:

• Absolute value of x is greater than 1.0 and y is −INFINITY ,

• absolute value of x is less than 1.0 and y is +INFINITY ,

• x is +INFINITY and y is less than 0.0. 

Sqrt returns +INFINITY when x is +INFINITY . 

ERRORS

Series 300
Exp returns HUGE_VAL when the correct value would overflow, or 0.0 when the correct value would underflow, and sets errno to ERANGE. 

Log and log10 return −HUGE_VAL and set errno to EDOM when x is non-positive.  A message indicating DOMAIN error (or SING error when x is 0.0) is printed on the standard error output. 

Pow returns 0.0 and sets errno to EDOM when x is 0.0 and y is non-positive, or when x is negative and y is not an integer.  In these cases a message indicating DOMAIN error is printed on the standard error output.  When the correct value for pow would overflow or underflow, pow returns ±HUGE_VAL or 0.0 respectively, and sets errno to ERANGE. 

Sqrt returns 0.0 and sets errno to EDOM when x is negative.  A message indicating DOMAIN error is printed on the standard error output. 

Series 800 (/lib/libm.a)
Exp returns HUGE_VAL when the correct value would overflow, or 0.0 when the correct value would underflow, and sets errno to ERANGE.  NaN is returned and errno is set to EDOM when x is NaN.  Log and log10 return −HUGE_VAL and set errno to EDOM when x is non-positive.  NaN is returned and errno is set to EDOM when x is NaN or −INFINITY .  A message indicating DOMAIN error (or SING error when x is 0.0) is printed on the standard error output in these cases. 

Pow returns 0.0 and sets errno to EDOM when x is 0.0 and y is negative, or when x is negative and y is not an integer.  NaN is returned and errno is set to EDOM when x or y is NaN.  In these cases a message indicating DOMAIN error is printed on the standard error output.  When the correct value for pow would overflow or underflow, pow returns ±HUGE_VAL or 0.0 respectively, and sets errno to ERANGE. 

Sqrt returns NaN and sets errno to EDOM when x is negative, NaN or −INFINITY .  A message indicating DOMAIN error is printed on the standard error output. 

Series 800 (ANSI C /lib/libM.a)
No error messages are printed on the standard error output.

Exp returns HUGE_VAL when the correct value would overflow, or 0.0 when the correct value would underflow, and sets errno to ERANGE .  NaN is returned and errno is set to EDOM when x is NaN. 

Log and log10 return NaN and set errno to EDOM when x is negative, −INFINITY, or NaN.  −HUGE_VAL is returned and errno is set to EDOM when x is 0.0. 

Pow returns −HUGE_VAL and sets errno to EDOM when x is 0.0 and y is negative.  NaN is returned and errno is set to EDOM when x is negative and y is not an integer or when x or y is NaN.  When the correct value for pow would overflow or underflow, pow returns ±HUGE_VAL or 0.0 respectively, and sets errno to ERANGE . 

Sqrt returns NaN and sets errno to EDOM when x is negative, NaN or −INFINITY . 

These error-handling procedures may be changed with the function matherr(3M).

SEE ALSO

hypot(3M), isinf(3M), isnan(3M), matherr(3M), sinh(3M). 

STANDARDS CONFORMANCE

exp: SVID2, XPG2, XPG3, POSIX.1, FIPS 151-1, ANSI C

log: SVID2, XPG2, XPG3, POSIX.1, FIPS 151-1, ANSI C

log10: SVID2, XPG2, XPG3, POSIX.1, FIPS 151-1, ANSI C

pow: SVID2, XPG2, XPG3, POSIX.1, FIPS 151-1, ANSI C

sqrt: SVID2, XPG2, XPG3, POSIX.1, FIPS 151-1, ANSI C

Hewlett-Packard Company  —  HP-UX 7.0 (Revised)