log

Date:

10-12-2011

NAME

LOG, ALOG, DLOG, CLOG, CDLOG - Compute natural logarithms

SYNOPSIS

LOG ([X=]x)
ALOG ([X=]x)
DLOG ([X=]x)
CLOG ([X=]x)
CDLOG ([X=]x)

IMPLEMENTATION

Cray Linux Environment (CLE)

STANDARDS

Fortran

Fortran extension: CDLOG

DESCRIPTION

LOG is the generic function name; the others are specifics. These are elemental intrinsic functions. They accept the following argument:

x

For ALOG and DLOG, x must be greater than zero and of type real. For CLOG and CDLOG, x must be of type complex and not equal to (0.,0.). The type and kind type of x is identical to the type and kind type of the return value. See the RETURN VALUES section for information on input data types and return values.

Vector versions of these intrinsics exist.

These functions evaluate y= ln(x).

CDLOG is called implicitly by as a result of a generic ALOG call with a complex double-precision argument.

NOTES

The ALOG, DLOG, and CLOG intrinsic function names can be passed as arguments; the others cannot.

The following return values occur:

  • ALOG(0) yields -infinity.

  • ALOG(-0) yields NaN.

  • If -infinity <= x< 0, ALOG(x) yields NaN.

  • ALOG(infinity) yields infinity.

Note: The log() function has a Linux-equivalent name. Use the man -aname option to show all manual pages matching name within the MANPATH search path. Manual pages are displayed in the order found.

RETURN VALUES

The generic function LOG becomes a call to one of the other functions depending on the type of its argument.

ALOG returns the real natural logarithm of its real argument.

DLOG returns the double-precision natural logarithm of its double-precision argument.

CLOG returns the complex natural logarithm of its complex argument. Its argument cannot equal (0.,0.). The range of the imaginary part is -pi < imaginary_part <= pi.

CDLOG returns the complex double-precision natural logarithm of its complex double-precision argument.