HP 3000 Manuals

Compiler Library/XL Reference Manual

DATAN (or DATAN') 

DATAN calculates the arctangent of a longreal number.

Declaration 

        FUNCTION DATAN(VAR x:LONGREAL):LONGREAL; EXTERNAL;

Accuracy 


Attributes 

Parameter:                A longreal number.

Result:                   A representable longreal number in the range
                          [-pi/2, pi/2].  See Chapter 1 for details on
                          the internal representation of longreal
                          numbers.

HP FORTRAN 77/XL:         Intrinsic function:  Y=DATAN(X).

Error:                    If the argument is a NaN, there are two cases.
                          If the INVALID trap is enabled, the message
                          "DATAN(X): X=NaN" occurs.  Otherwise, the
                          INVALID flag is set.  In either case, a quiet
                          NaN is returned.

Special Values 

                 datan (+Infinity) = pi/2

                 datan (-Infinity) = -pi/2

MPE/iX 5.0 Documentation