`remove_if` removes from `rng` all of the elements `x` for which `pred(x)` is `true`. The versions of `remove_if` that return an iterator, return an iterator `new_last` such that the range `[begin(rng), new_last)` contains no elements where `pred(x)` is `true`. The iterators in the range `[new_last, end(rng))` are dereferenceable, but the elements are unspecified.
[heading Definition]
Defined in the header file `boost/range/algorithm/remove_if.hpp`
[heading Requirements]
* `ForwardRange` is a model of the __forward_range__ Concept.
* `ForwardRange` is mutable.
* `UnaryPredicate` is a model of the `PredicateConcept`.
* `ForwardRange`'s value type is convertible to `UnaryPredicate`'s argument type.
[heading Complexity]
Linear. `remove_if` performs exactly `distance(rng)` applications of `pred`.
