2.4.1 atan2() Interface

The interface to the atan2() routine is:

F_TYPE atan2 (F_TYPE y, F_TYPE x)

The routine name atan2() is the high-level language source-level name that gets mapped to a specific entry-point name documented in Appendix B. This is the name that appears in compiler documentation for this mathematical routine. The appropriate entry-point name is automatically selected when atan2() is called from high-level language syntax. This selection depends upon the data type of the input arguments. If you make direct calls to this routine, you must manually select the proper entry-point name documented in Appendix B for the data type of your input arguments.

The format of the atan2() routine shows that it expects to receive two input arguments by value. Both arguments must be the same F_ TYPE. The returned value will also be the same F_TYPE as the input arguments.

For example, on OpenVMS Alpha systems, the G_FLOAT entry-point name is math$atan2_g(). It takes two G_FLOAT arguments by value and returns a G_FLOAT result.

For Digital UNIX Alpha systems, the S_FLOAT entry-point name is atan2f(). The routine takes two S_FLOAT input arguments by value and returns an S_FLOAT result.