Changes or voids default typing rules.
Syntax
The IMPLICIT
statement can take either of the following forms:
First form:
IMPLICIT type (range-list)[, type (range-list) ,]... |
- type
is the data type to be associated with the corresponding
letters in range-list.
- range-list
is a comma-separated list of letters or ranges of
letters (for example, A-Z
or I-N) to be
associated with type. Writing a range
of letters has the same effect as writing a list of single letters.
Description
The IMPLICIT
statement can be used either to change or void the default typing
rules within the program unit in which it appears, depending on
which of the two forms the statement takes.
First form
This form of the IMPLICIT
statement specifies type as the data
type for all variables, arrays, named constants, function subprograms,
ENTRY names in
function subprograms, and statement functions that begin with any
letter in range-list and that are not
explicitly given a type.
Within the specification statements of a program unit, IMPLICIT
statements must precede all other specification statements, except
possibly the DATA
and PARAMETER
statements.
The same letter must not appear as a single letter or be included
in a range of letters, more than once in all of the IMPLICIT
statements in a scoping unit.
For information on how the IMPLICIT
and PARAMETER
statements interact, refer to “PARAMETER (statement and attribute)”.
Second form
The IMPLICIT NONE
statement disables the default typing rules for all variables, arrays,
named constants, function subprograms, ENTRY
names, and statement functions (but not intrinsic functions). All
such objects must be explicitly typed. The IMPLICIT NONE
statement must be the only IMPLICIT
statement in the scoping unit, and it must precede any PARAMETER
statement. Types of intrinsic functions are not affected.
You can also use the +implicit_none
compile-line option to void the default typing rules. A program
compiled with this option may include IMPLICIT
statements, which the compiler will honor.
Examples
The following statement causes all variables and function
names beginning with I,
J, or K
to be of type complex, and all data items beginning with A,
B, or C
to be of type integer:
IMPLICIT COMPLEX (I, J, K), INTEGER (A-C) |
Related concepts
For related information, see the following:
Printable version
