chap14 - Chapter 14 Chapter Templates and Polymorphism Generic functions and classes Polymorphic Functions What are they Generic functions that can act

# chap14 - Chapter 14 Chapter Templates and Polymorphism...

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Chapter 14 Chapter 14 Templates and Polymorphism Generic functions and classes
Polymorphic Functions What are they? Generic functions that can act upon objects of different types The action taken depends upon the types of the objects Where have we seen them before? Function overloading Define functions or operators with the same name Rational addition operator + Function Min() for the various numeric types Primitive polymorphism
Polymorphic Functions Templates Generate a function or class at compile time Where have we seen them before? Standard Template Library Vector and other container classes True polymorphism Choice of which function to execute is made during run time C++ uses virtual functions
Function Overloading We rewrite functions Min(), Max(), and Sort() for many different types int Min( int a, int b) { if (a < b) return a; else return b; } double Min( double a, double b) { if (a < b) return a; else return b; } Rational Min(Rational a, Rationalb) { if (a < b) return a; else return b; } There has to be a better way!
Function Templates Function template Describes a function format that when instantiated with particulars generates a function definition Write once, use multiple times template < class T> T Min( const T &a, const T &b) { if (a < b) return a; else return b; } Indicates a template is being defined T is a formal template type parameter
Template Function Code segment int Input1 = PromptAndRead(); int Input2 = PromptAndRead(); cout << Min(Input1, Input2) << endl; Causes the following function to be generated from our template int Min( const int &a, const int &b) { if (a < b) return a; else return b; }
Template Function Code segment double Value1 = 4.30; double Value2 = 19.54; cout << Min(Value1, Value2) << endl; Causes the following function to be generated from our template double Min( const double &a, const double &b) { if (a < b) return a; else return b; }
Template Function Code segment Rational r(6,21); Rational s(11,29); cout << Min(r, s) << endl; Causes the following function to be generated from our template Rational Min( const Rational &a, const Rational &b) { if (a < b) return a; else return b; } Operator < needs to be defined for the actual template parameter type. If < is not defined, then a compile-time error occurs

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