Difference Between Function and Predicate In Alloy 4? -


i'm having hard time understanding difference between predicates , functions in alloy 4. i've read section 4.5.2 in software abstractions it's still not clear me. can me understand?

a function represents parameterized expression gets inlined @ every invocation site.

a predicate represents formula, i.e., boolean expression, in sense kind of function returns boolean expression. difference in alloy can "run" , "check" predicates, using alloy "run" , "check" commands. running predicate instructs alloy find model predicate holds, whereas checking predicate instructs alloy check if there exists model predicate not hold.


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