Modern C++ Programming Cookbook

How it works...

The expression for the range-based for loops shown earlier in the How to do it... section is basically syntactic sugar as the compiler transforms it into something else. Before C++17, the code generated by the compiler used to be the following:

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

What begin_expr and end_expr are in this code depends on the type of the range:

• For C-like arrays, __range and __bound are the number of elements in the array.
• For a class type with begin() and end() members (regardless of their type and accessibility): __range.begin() and __range.end().
• For others it is begin(__range) ...