CSCE 121- Spring 2016 J. Michael Moore

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Presentation transcript:

CSCE 121- Spring 2016 J. Michael Moore Type Safety CSCE 121- Spring 2016 J. Michael Moore

Type Safety Every object will be used only according to its type Variable is only used after it is initialized Only operations defined for the variables type will be applied Every operation defined for a variable results in a valid value IDEAL! Static type safety Compiler finds all type safety violations. IDEAL! Dynamic type safety Run-time system finds all safety violations not found by compiler

Type Safety Important! C++ not completely statically type safe Try hard not to violate Compiler can help C++ not completely statically type safe Most languages are not Reduces ability to express ideas C++ is not completely dynamically type safe Many languages are, but… Being dynamically type safe can cause performance problems Most things in class will be type safe

Type Conversion Implicit conversion Explicit conversion One type automatically converted to another type BEWARE!!! Explicit conversion While not recommended almost everything can be cast

Mostly Safe Conversions “Widening” conversions long int x = 112233445566778899; double y = x; // loss of precision char b = 'k'; int a = b; // a is numerical representation of b, but no loss of information

Unsafe Conversions “Narrowing” conversions double x = 2.7; int y = x; // truncation int a = 1000; char b = a; How to ‘outlaw’ unsafe conversions? See Stroustrup book. (Possible test question…)