alog(3M)

NAME
     ALOG, DLOG, CLOG, CDLOG - Computes natural logarithm

SYNOPSIS
     UNICOS and UNICOS/mk systems:

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

     UNICOS and IRIX systems:
     CDLOG ([X=]x)

IMPLEMENTATION
     UNICOS, UNICOS/mk, and IRIX systems

STANDARDS
     Fortran 90
     CDLOG is a compiler extension to Fortran 90.

DESCRIPTION
     LOG is the generic function name.  ALOG, DLOG, and CLOG are intrinsic
     and elemental functions for CF90.

     A vector version of this intrinsic exists on UNICOS and UNICOS/mk
     systems.  On UNICOS/mk systems, the vector version of this intrinsic
     is used when -h vector3 (C compiler) or -O vector3 or -O3 (Fortran
     compiler) has been specified on the compiler command line.

     The entry point CDLOG is provided for support in other languages.  It
     is not recognized as an intrinsic function; therefore, you must use
     the CDIR$ VFUNCTION directive to allow vectorization.

     These functions evaluate y = ln(x).

   CF90
     CDLOG is called implicitly by the Fortran 90 compiler as a result of a
     generic ALOG call with a complex double-precision argument.

   CAL Register Usage (Cray Research Systems Only)
     Scalar ALOG:  ALOG% (call-by-register)
          on entry   (S1) = argument
          on exit    (S1) = result

     Vector ALOG:  %ALOG% (call-by-register)
          on entry   (V1) = argument vector
          on exit    (V1) = result vector

     Scalar DLOG:  DLOG% (call-by-register)
          on entry   (S1) and (S2) = argument
          on exit    (S1) and (S2) = result

     Vector DLOG:  %DLOG% (call-by-register)
          on entry   (V1) and (V2) = argument vector
          on exit    (V1) and (V2) = result vector

     Scalar CLOG:  CLOG% (call-by-register)
          on entry   (S1) and (S2) = argument
          on exit    (S1) and (S2) = result

     Vector CLOG:  %CLOG% (call-by-register)
          on entry   (V1) and (V2) = argument vector
          on exit    (V1) and (V2) = result vector

     Scalar CDLOG:  CDLOG% (call-by-register)
          on entry   (S1), (S2), (S3), (S4) = argument
          on exit    (S1), (S2), (S3), (S4) = result

     Vector CDLOG:  %CDLOG% (call-by-register)
          on entry   (V1), (V2), (V3), (V4) = argument vector
          on exit    (V1), (V2), (V3), (V4) = result vector

   Argument Range                2450
     infinity is approximately 10
                                                       308
     On UNICOS/mk systems, infinity is approximately 10

     ALOG, DLOG:  0 < x < infinity

     CLOG:  x must not be (0,0).

     CDLOG (all systems except UNICOS/mk systems):  x must not be (0,0).

NOTES
     CDLOG is an outmoded routine for CF90.  Refer to the Fortran Language
     Reference Manual, Volume 3, publication SR-3905, for information about
     outmoded features and their preferred standard alternatives.

     The name of the ALOG, DLOG, and CLOG intrinsic can be passed as an
     argument.  The name of the CDLOG intrinsic cannot be passed as an
     argument.

RETURN VALUES
     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.

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

     On CRAY T90 systems that support IEEE arithmetic, the following return
     values occur:

          ALOG(0) = - infinity

          ALOG(-0) = NaN

          ALOG(x) = NaN if - infinity <= x < 0

          ALOG( infinity ) = infinity

SEE ALSO
     Intrinsic Procedures Reference Manual, publication SR-2138, for the
     printed version of this man page.