HP Fortran Programmer's Reference (September 2007)

Intrinsic procedures
Intrinsic procedure specifications
Chapter 11 527
Arguments
POINTER must be a pointer and may be of any type. Its pointer association status
must not be undefined.
TARGET (optional) must be a pointer or target. If it is a pointer, its pointer association status
must not be undefined.
Result type
The result is scalar of type default logical.
Result value
Case 1 If TARGET is absent, the result is .TRUE. if POINTER is currently associated
with a target and .FALSE. if it is not.
Case 2 If TARGET is present and is a target, the result is .TRUE. if POINTER is
currently associated with TARGET and .FALSE. if it is not.
Case 3 If TARGET is present and is a pointer, the result is .TRUE. if both POINTER
and TARGET are currently associated with the same target, and is .FALSE.
otherwise. If either POINTER or TARGET is disassociated, the result is
.FALSE..
ATAN(X)
Description
Arctangent (inverse tangent) function in radians.
Class
Elemental function.
Argument
X must be of type real.
Result type/
type parameters
Same as X.