IEEE_IS_NAN(X)

Type

An elemental IEEE function. Tests whether a value is IEEE Not-a-Number. Returns true if IEEE_CLASS(X) has the value IEEE_SIGNALING_NAN or IEEE_QUIET_NAN. It returns false otherwise.

Module

IEEE_ARITHMETIC

Syntax

Where X is of type real.

Result type and attributes

Where the result is of type default logical.

Rules

To ensure compliance with the Fortran 2003 standard, the IEEE_SUPPORT_DATATYPE(X) and IEEE_SUPPORT_NAN(X) must return with a value of true.

Examples

Example 1:

USE, INTRINSIC :: IEEE_ARITHMETIC
REAL :: X = -1.0
IF (IEEE_SUPPORT_DATATYPE(X)) THEN
  IF (IEEE_SUPPORT_SQRT(X)) THEN    ! IEEE-compliant SQRT function
    IF (IEEE_SUPPORT_NAN(X)) THEN
      PRINT *, IEEE_IS_NAN(SQRT(X)) ! Prints true
    ENDIF
  ENDIF
ENDIF

Example 2:

USE, INTRINSIC :: IEEE_ARITHMETIC
REAL :: X = -1.0
IF (IEEE_SUPPORT_STANDARD(X)) THEN
  PRINT *, IEEE_IS_NAN(SQRT(X))     ! Prints true
ENDIF