8.14 Fortran 90 Features

For convenience this section collects a list (probably incomplete) of the Fortran 90 features supported by the GNU Fortran language, even if they are documented elsewhere. See section `Characters' in and Execution Sequence, for information on additional fixed source form lexical issues. Further, the free source form is supported through the `-ffree-form' option. Other Fortran 90 features can be turned on by the `-ff90' option; see 9.7 Fortran 90. For information on the Fortran 90 intrinsics available, see 8.11.9 Table of Intrinsic Functions.

Automatic arrays in procedures

Character assignments

In character assignments, the variable being assigned may occur on the right hand side of the assignment.

Character strings

Strings may have zero length and substrings of character constants are permitted. Character constants may be enclosed in double quotes (") as well as single quotes. See section 8.7.4 Character Type.

Construct names

(Symbolic tags on blocks.) See section 8.10.3 Construct Names.

CYCLE and EXIT

See section The CYCLE and EXIT Statements.

DOUBLE COMPLEX

See section DOUBLE COMPLEX Statement.

DO WHILE

See section 8.10.1 DO WHILE.

END decoration

See section 8.6.4 Statements.

END DO

See section 8.10.2 END DO.

KIND

IMPLICIT NONE

INCLUDE statements

See section 8.6.7 Including Source Text.

List-directed and namelist I/O on internal files

Binary, octal and hexadecimal constants

These are supported more generally than required by Fortran 90. See section 8.7.3 Integer Type.

`O' and `Z' edit descriptors

NAMELIST

See section 8.9.1 NAMELIST Statement.

OPEN specifiers

STATUS='REPLACE' is supported. The FILE= specifier may be omitted in an OPEN statement if STATUS='SCRATCH' is supplied.

FORMAT edit descriptors

The Z edit descriptor is supported.

Relational operators

The operators <, <=, ==, /=, > and >= may be used instead of .LT., .LE., .EQ., .NE., .GT. and .GE. respectively.

SELECT CASE

Not fully implemented. See section SELECT CASE on CHARACTER Type.

Specification statements

A limited subset of the Fortran 90 syntax and semantics for variable declarations is supported, including KIND. See section 8.7.1.3 Kind Notation. (KIND is of limited usefulness in the absence of the KIND-related intrinsics, since these intrinsics permit writing more widely portable code.) An example of supported KIND usage is:

INTEGER (KIND=1) :: FOO=1, BAR=2 CHARACTER (LEN=3) FOO

PARAMETER and DIMENSION attributes aren't supported.