• []Rationale. These statements are allowed in a FORALL construct because they are defined as forms of assignment in Fortran 90 and HPF. The intent is that forall-construct, like forall-stmt, is a block assignment rather than a general-purpose ``parallel loop.'' (End of rationale.)

To determine the set of permitted values for an index-name, we introduce some simplifying notation. In the forall-triplet-spec, let

• be the first subscript (``lower bound'');

• be the second subscript (``upper bound'');

• be the stride; and

• be .

If stride is missing, it is as if it were present with the value 1. The set of permitted values is determined on entry to the construct and is , . The expression stride must not have the value 0. If for some index-name , no forall-body-stmt is executed.

Each assignment nested within a FORALL construct assigns to memory locations specified by the forall-assignment for permitted values of the index-name variables. A program that causes multiple values to be assigned to the same location by a single statement is not HPF-conforming and therefore has no defined meaning. An HPF-conforming program may, however, assign to the same location in syntactically different assignment statements. This is a semantic constraint rather than a syntactic constraint, however; in general, it cannot be checked during compilation.