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##### Functions

Expression | Return type | Returns | Complexity
--- | --- | --- | ---
`begin(x)` | `range_iterator<X>::type` | `p.first` if `p` is of type `std::pair<T>` `a` if `a` is an array `range_begin(x)` if that expression would invoke a function found by ADL `t.begin()` otherwise | constant time
`end(x)` | `range_iterator<X>::type` | `p.second` if `p` is of type `std::pair<T>` `a + sz` if `a` is an array of size `sz` `range_end(x)` if that expression would invoke a function found by ADL `t.end()` otherwise | constant time
`empty(x)` | `bool` | `boost::begin(x) == boost::end(x)` | constant time
`distance(x)` | `range_difference<X>::type` | `std::distance(boost::begin(x),boost::end(x))` | -
`size(x)` | `range_difference<X>::type` | `range_calculate_size(x)` which by default is `boost::end(x) - boost::begin(x)`. Users may supply alternative implementations by implementing `range_calculate_size(x)` so that it will be found via ADL | constant time
`rbegin(x)` | `range_reverse_iterator<X>::type` | `range_reverse_iterator<X>::type(boost::end(x))` | constant time
`rend(x)` | `range_reverse_iterator<X>::type` | `range_reverse_iterator<X>::type(boost::begin(x))` | constant time
`const_begin(x)` | `range_iterator<const X>::type` | `range_iterator<const X>::type(boost::begin(x))` | constant time
`const_end(x)` | `range_iterator<const X>::type` | `range_iterator<const X>::type(boost::end(x))` | constant time
`const_rbegin(x)` | `range_reverse_iterator<const X>::type` | `range_reverse_iterator<const X>::type(boost::rbegin(x))` | constant time
`const_rend(x)` | `range_reverse_iterator<const X>::type` | `range_reverse_iterator<const X>::type(boost::rend(x))` | constant time
`as_literal(x)` | `iterator_range<U>` where `U` is `Char*` if `x` is a pointer to a string and `U` is `range_iterator<X>::type` otherwise | `[s,s + std::char_traits<X>::length(s))` if `s` is a `Char*` or an array of `Char` `[boost::begin(x),boost::end(x))` otherwise | linear time for pointers to a string or arrays of `Char`, constant time otherwise
`as_array(x)` | `iterator_range<X>` | `[boost::begin(x),boost::end(x))` |

The special `const_`-named functions are useful when you want to document clearly that your code is read-only.

`as_literal()` can be used internally in string algorithm libraries such that arrays of characters are handled correctly.

`as_array()` can be used with string algorithm libraries to make it clear that arrays of characters are handled like an array and not like a string.

Notice that the above functions should always be called with qualification (`boost::`) to prevent unintended Argument Dependent Lookup (ADL).