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Functions
And
Subroutines
5-2
I f
the
name
of
an
intrinsic
function
appears
in the
dummy
argument
list
of
a
FUNC-
TION
or
SUBROUTINE
subprogram,
the
name
is
considered
to
have
no
relation
to
the intrinsic
function
within the scope
of
the
program
unit
and
the
name
itself loses
its intrinsic quality.
The
data
type associated with the symbolic
name
is
specified as
normal
(by
default
or
by a type
statement).
If
the
name
of
an
intrinsic
function
is
to be used as
an
actual
argument
in
an
external
procedure
reference, the
name
must
first be specified in
an
INTRINSIC
statement.
5.1.2 I NTRI NSIC Statement
The
INTRINSIC
statement
confirms
that
a symbolic
name
represents
an
intrinsic
function
and
allows
that
name
to
be used as
an
actual
argument.
Only
one
ap-
pearance
of
a symbolic
name
in all
of
the
INTRINSIC
statements
in a given
program
unit
is
allowed. A symbolic
name
may
not
appear
in
an
INTRINSIC
statement
and
an
EXTERNAL
statement
in the
same
program
unit.
The
format
of
the
INTRINSIC
statement
is
INTRINSIC
tunc
[,tunc]
...
where
'func'
is
an
intrinsic function
name.
The
names
of
certain
intrinsic
functions
cannot
be used as
actual
arguments
and,
therefore,
cannot
appear
in
INTRINSIC
statements.
These
are
the functions for
type conversion
(lNT,
IFIX,
FLOAT,
REAL,
ICHAR)
and
the functions for choos-
ing a largest
or
smallest value (MAXO,
AMAXI,
AMAXO,
MAXI,
MINO,
AMINI,
AMINO,
MINI).
Examples:
INTRINSIC
SQRT
INTRINSIC
EXP, LOG, LOG10
5.1.3 Statement Functions
Straightforward
mathematical
functions
like
f(x)
= ax
2
+
bx
+ c
are
defined
in
FORTRAN
using
statement
functions.
These
functions
have
no
keyword;
the
format
is
tunc
([dum [,dum]
...
])
= exp
where
June
is
the symbolic
name
of
the
statement
function
dum
is
a
dummy
argument
to
be replaced by
an
actual
argument
when
the
function
is
referenced
exp
is
an
expression
As
an
example,
the
mathematical
function
above
would
be
written
F(X) =
A*(X**2)+
8*X
+ C
Substituting
the
actual
argument
'3'
for
the
dummy
argument
'X'
in this
function
would
result in the value
'9A
+ 3B +
C.'
FORTRAN-SO