The ENFORCE statement
Purpose
The purpose of this statement is to automatically modify the population of a relation based on rules.
Syntax
Since ampersand 4.4.0 the syntax of this statement is:
The <operator> can be one of :=
, :<
or >:
.
This statement may occur anywhere within a context, either inside or outside a pattern.
Semantics
This statement means the population of the relation will automatically be kept respectively equal ( :=
), a subset (:<
) or a superset (>:
) of the population of the given term.
Examples
Miscellaneous
Both the sources and the targets of the relation and the term must match. An error message is given otherwise.
The relation must be specified in order to use it here, as is the case with any relation used in an expression.
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