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In this pattern, predicate must be an expression evaluating to a single argument function. This pattern matches if predicate applied to the corresponding value is true, and the subpatterns all match. The predicate should not have side effects, as the code generated by the pattern matcher may invoke predicates repeatedly in any order. The predicate expression is bound in the same scope as the match expression, ie., free variables in predicate are not bound by pattern variables.



PLT