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
