6.3.1.1 Generic References to Intrinsic Functions

Many of the Fortran intrinsic functions have generic (or common) names. If you refer to an intrinsic function by using its generic name, the selection of the library routine is based on the data type of the argument in the function reference.

For example, the generic name COS lists five intrinsic functions that calculate cosines: COS, DCOS, QCOS (VMS, U*X), CCOS, and CDCOS. These functions return different values: REAL*4, REAL*8, REAL*16 (VMS, U*X), COMPLEX*8, and COMPLEX*16, respectively.

To invoke the cosine function, you can refer to it generically as COS. The compiler then selects the appropriate routine, based on the arguments that you specify. For example, if the argument is REAL*4, COS is selected; if it is REAL*8, DCOS is selected; and if it is COMPLEX*8, CCOS is selected.

You can also explicitly refer to a particular routine. For example, to invoke the double-precision cosine function, you could specify DCOS rather than use the generic name.

The compiler lists the internal names of the intrinsic functions it has selected in the "FUNCTIONS AND SUBROUTINES REFERENCED" section of the source code listing.

Function selection occurs independently for each generic reference, so you can use a generic reference repeatedly in the same program unit to access different intrinsic functions.

Table 6-3 lists generic intrinsic function names. However, you cannot use the names in this table to generically select intrinsic functions if you use them in any of the following ways:

• As the name of a statement function

• As a dummy argument name, a common block name, or a variable or array name

Using the generic name of an intrinsic function in an INTRINSIC statement does not affect function references. However, when you use a generic function name in an actual argument list as the name of a function to be passed, function selection does not occur because there is no argument list on which to base a selection. The generic name is treated according to the rules for handling specific intrinsic function names (see Section 6.3).

Generic function names are local to the program unit that refers to them, so they can be used for other purposes in other program units.

Table 6-3 Summary of Generic Intrinsic Function Names

For More Information:

• On the INTRINSIC statement, see Section 4.10.

• On generic and specific intrinsic functions, see Section C.2.

• On compiler options, in general, see your user manual.

• On names of compiler options used in this manual, see Section E.4.