Template Classes and Functions in C++

Question

I have a question that confuses me. I know what is template and aim of it but I have some blank points on usage.

I have a Template class like that:

template <class elemType>
class SSorting {
public:

int seqSearch(const elemType list[], int length, const elemType& item);
};

When I code the member of a class function seqSearch I need to declare as:

template <class elemType>
int SSorting <elemType> :: seqSearch(const elemType list[], int length, const elemType& item){
    *statements*
}

Everything okay at this point. template says this is a function that inside a template class and int in front of the function means that the function will return an integer value, but the part that I don't understand is why we have to write SSorting <elemType> :: seqSearch instead of SSorting :: seqSearch. I already say this is a member of a template class and return type why I we need to say <elemType> again.

score 1 · Accepted Answer · edited Apr 03 '20 at 14:08

1

You should recall that class/function templates means that for each instantiation with a different template type, the compiler writes down another copy of the code, replacing elemType with the relevant type. Meaning, that if you are using in your code both SSorting<double> and SSorting<int>, you get two totally different types, with different names.

Thus, the name of the class isn't SSorting, but SSorting<elemType>!

edited Apr 03 '20 at 14:08

463035818_is_not_an_ai

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answered Apr 03 '20 at 13:19

Kerek

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If you think that this answer is correct (and answers your question), you should accept it, or at least upvote it – Kerek Apr 03 '20 at 13:24
1

same nitpick here: correct term is "class template" not "template class" (and "function templates" not "template functions") – 463035818_is_not_an_ai Apr 03 '20 at 13:30
@idclev463035818 fixed – Kerek Apr 03 '20 at 14:07
fixed the fix ;) – 463035818_is_not_an_ai Apr 03 '20 at 14:08
@idclev463035818 Excuse me for my bad grammar XD – Kerek Apr 03 '20 at 14:12

score 0 · Answer 2 · answered Apr 03 '20 at 13:27

0

Template class is not a "real" class, it is template code. It does not exist until you use it. When you do not write "elemType" part in the definition part, you're just defining a member function of "real" class.

answered Apr 03 '20 at 13:27

Kor Sar

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there are no template classes you mean "class template" – 463035818_is_not_an_ai Apr 03 '20 at 13:30
@walnut Yeah i know, i think im just generally confused by what they mean here :D – Object object Apr 03 '20 at 13:44

Template Classes and Functions in C++

2 Answers2