EXTERNAL and INTRINSIC Statements EXTERNAL statement is used to name external procedures which are
required in order to run a given program unit. It may specify the name of
any external function or subroutine. It is required in three rather different
circumstances:
INTRINSIC statement is used to declare a name to be that of an intrinsic
function. It is normally necessary only when that function is to be used as the actual
argument of another procedure call, but may also be advisable when calling a
non-standard intrinsic function to remove any ambiguity which might arise if an
external function of the same name also existed.
The general form of the two statements is the same:
EXTERNAL ename, ename, ... ename
INTRINSIC iname, iname, ... iname
Where ename can be the name of an external function or subroutine or a dummy
procedure; iname must be specific name of an intrinsic function. For example, to use
the real and double precision versions of the trigonometric functions as actual
arguments we need:
INTRINSIC SIN, COS, TAN, DCOS, DSIN, DTAN
When the function name SIN is used as an actual argument it refers to
the specific real sine function; in other contexts it still has its usual generic
property. The use of procedures as actual arguments is covered in detail
in section 9.7; a list of specific names of intrinsic functions is given in the
appendix.
