Type Checking A compiler has to do semantic checks in addition to syntactic checks ● Semantic Checks Static-done during compilation -Dynamic-done during run-time Type checking is one of these static checking operations we may not do all type checking at compile-time -Some systems also use dynamic type checking too. A type system is a collection of rules for assigning type expressions to the parts of a program. A type checker implements a type system. A sound type system eliminates run-time type checking for type errors. A programming language is strongly-typed,if every program its compiler accepts will execute without type errors. In practice,some of type checking operations are done at run-time(so,most of the programming languages are not strongly-typed). Ex:int x[100];...x[i]>most of the compilers cannot guarantee that i will be between 0 and 99 CS308 Compiler Theory 8Type Checking • A compiler has to do semantic checks in addition to syntactic checks. • Semantic Checks Semantic Checks – Static – done during compilation – Dynamic – done during run-time • T h ki ype checking is one of these static checking operations is one of these static checking operations. – we may not do all type checking at compile-time. – Some systems also use dynamic type checking too. • A t t ype system i ll ti f l f i i t i t th t f is a collection of rules for assigning type expressions to the parts of a program. • A type checker implements a type system. • A sound type system eliminates run-time type checking for type errors. • A programming language is strongly-typed, if every program its compiler accepts will execute without type errors. – In practice, some of type checking operations are done at run-time (so, most of the programming languages are not strongly-typed). – Ex: int x[100]; … x[i] Î most of the compilers cannot guarantee that i will be between 0 and 99 CS308 Compiler Theory 8