Default Arguments in a Template Instantiation

Default Arguments in a Template Instantiation

Templates can have default type parameters. The compiler uses these default types when you don’t provide them explicitly in a template instantiation. For example:

 template < class T1=char, class T2=char > // default typesclass E { public:  E( T1 t1, T2 t2 ) {m1=t1; m2=t2; } private:  T1 m1;  T2 m2;};

You instantiate a template with default type parameters like this:

 int main(){ E  e1(0,0);//OK, explicit types provided E <> e2('a','b');//OK, using default types}

Make sure that your template instance has a pair of empty angular brackets after the template’s name when you create a template instance that uses default type values.Omitting the empty pair of angular brackets, as in the following declaration, is an error:

 E e3('a','c');   //compilation error; <> missing
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