Question

The latest C++ 11 specification defines a new type of for loop called “range-based for loop”.
Its looks and mechanics appear to be pretty much identical to the for-each loops available in other languages.

What are the differences between the two of them, if any? If there are no differences why the new name?

Edit: To clarify, I’m not looking for implementation differences between the “range based for” of c++ and other languages’ for each or std::for_each. Instead I was wondering if there was some hidden value behind the fact that they decided to call this new c++ “feature” (or syntax, or idiom or whatever you want to call it) “range-based for loop” instead of “for each loop” as pretty much anyone else seems to be calling these things.

Answer 1

Syntax:

for ( range_declaration : range_expression) loop_statement  

produces code equivalent to:

{
    auto && __range = range_expression ; 
    auto __begin = begin_expr(__range); 
    auto __end = end_expr(__range); 
    for (;__begin != __end; ++__begin) { 
        range_declaration = *__begin; 
        loop_statement 
    } 
} 

While the std::for_each applies unary function to the specified range. So, there are two basic differences:

• The range-based for-loop syntax is cleaner and more universal, but you can’t execute the code in loop for a specified range different than from begin() to end().
• Range-based for-loop can be applied to containers which don’t have iterators defined, by defining begin() and end() functions.

You cannot compare it to the “generalized for-each idiom”, because there is no standard idiom. To compare, you have to point out the concrete implementation and the difference is usually hidden in the details.