Why does string::find return size_type and not an

Question

In C++, why does string::find return size_type and not an iterator?

It would make sense because functions like string::replace or string::insert take iterators as input, so you could find some character and immediately pass the returned iterator to replace, etc.

Also, std::find returns an iterator -- why is std::string::find different?

Answer 1

It's probably more useful to get a number from find because then you can use the [] operator or substr() to get to the characters you just searched for are.

Also, if you want an iterator, you can always do begin() + pos

Answer 2

All the string functions operate on indexes, some functions (like replace() and insert()) just additionally support iterators. So the result of find() can directly be used in those functions. Since there can't be two find() functions that just differ by return type (one returning an iterator, one returning an index) one had to be chosen.

Answer 3

The design of the standard library's shiny new string class was already done when Stroustrup introduced the standard committee to the STL. The committee liked the STL and started incorporating it into the standard, thereby adapting much of what they had already agreed on (and probably also delaying the standard for another year or two).

Among other changes, iterators were added to the already finished string class as an after-thought. You can see this by looking at the various string members taking/returning a position – it's a wild mix of indexes and iterators.

It's not always easy to guess why some member functions have only indices-taking versions and some have iterator-taking ones, too. In the case of std::basic_string<>::find(), however, it seems easy: Since std::find() already returns an iterator, std::basic_string<>::find() was left as it was.

Answer 4

I assume it's because in general string members work on indexes rather than iterators and this makes it easy to use the returned value. You can always use std::find if you want to get an iterator.