Language Reference

SIGN(A, B)

Returns the absolute value of A times the sign of B. If A is non-zero, you can use the result to determine whether B is negative or non-negative, as the sign of the result is the same as the sign of B.

Note that if you have declared B as REAL(4) or REAL(8), and B has a negative zero value, the sign of the result depends on whether you have specified the -qxlf90=signedzero compiler option.

A

must be of type integer or real.

B

must be of the same type and kind type parameter as A.

Class

Elemental function

Result Type and Attributes

Same as A.

Result Value

The result is sgn*|A|, where:

• sgn = -1, if either of the following is true:
  • B < 0

    +-------------------------------IBM Extension--------------------------------+

    
    
  • B is a REAL(4) or REAL(8) number with a value of negative 0, and you have specified the -qxlf90=signedzero option

    +----------------------------End of IBM Extension----------------------------+

• sgn = 1, otherwise.

+---------------------------------Fortran 95---------------------------------+

Fortran 95 allows a processor to distinguish between a positive and a negative real zero, whereas Fortran 90 did not. Using the -qxlf90=signedzero option allows you to specify the Fortran 95 behavior (except in the case of REAL(16) numbers), which is consistent with the IEEE standard for binary floating-point arithmetic. -qxlf90=signedzero is the default for the xlf95, xlf95_r, and xlf95_r7 invocation commands.

+-----------------------------End of Fortran 95------------------------------+

Examples

SIGN (-3.0, 2.0) has the value 3.0.

Notes:

1. IBM Extension: the ability to specify a nondefault integer argument.

2. IBM Extension: the ability to pass the name as an argument.

Related Information

See the "-qxlf90 Option" in the User's Guide.