(j3.2006) Interface and PURE

[Bill Long]

In 15.4.3.2 Interface block (page 305), para 7, we say:

"If an explicit specific interface for an external procedure is specified by an interface body or a procedure declaration statement (15.4.3.6), the characteristics shall be consistent with those specified in the procedure definition, except that the interface may specify a procedure that is not pure even if the procedure is defined to be pure.?

With prefix choices of IMPURE,  PURE, and neither, there are 9 possibilities:

OK combinations:
???????????

Procedure definition: PURE,  Interface: PURE
Procedure definition: PURE,  Interface: IMPURE
Procedure definition: PURE,  Interface: (none specified)
Procedure definition: IMPURE, Interface: IMPURE
Procedure definition: (none specified), Interface (none specified)

BAD combinations:
????????????

Procedure definition: IMPURE, Interface: PURE
Procedure definition: (none specified), Interface: PURE

Questionable combinations:
??????????????????

Procedure definition: IMPURE, Interface : (none specified)
Procedure definition: (none specified), Interface IMPURE


The OK group are clearly allowed. The BAD group are clearly disallowed (and dangerous).  For ?Questionable? group, are IMPURE and ?none specified? considered ?consistent? for the purposes of this paragraph? (Except for the case of an ELEMENTAL procedure where ?none specified? is equivalent to PURE.)  Or are those two options also considered errors?

Cheers,
Bill


Bill Long                                                                       longb at cray.com
Principal Engineer, Fortran Technical Support &   voice:  651-605-9024
Bioinformatics Software Development                      fax:  651-605-9143
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