Friday, April 17, 2009

iterator arg to STL find() can be anything

Suppose I get a vector<int>::iterator from a vector<int> begin().
Suppose I get a list<int>::iterator from a list<int> begin().

Now, these 2 objects don't have a common super class[1]. But somehow, find() can use either object as its first argument. Find() can even use a qq(int *) object as its first argument. However, find() can't accept a "float" object as first argument. I guess compiler will not complain, until you deference the iterator. I think find() does that.

Suppose I get a vector<int>::reverse_iterator from a vector<int> rbegin() - call it vec_r_it. Can I pass it to find? I think find() is going to increment it and deference it.

[1] array-based containers' iterators are pointers, not wrapped into some wrapper object. Linked list, map, set ... define real classes for their iterators.

In Java, the param to such a find() would be an interface, or a template param T like < T extends SomeInterface>. In java, such an "expected-service" is always ("clean" language) expressed using interfaces. C++ is more complicated and flexible.

C# has a bunch of iteration constructs, not as "clean" as java.

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