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## Class optional_last_value<void>

boost::signals2::optional_last_value<void> — Evaluate an InputIterator sequence.

## Synopsis

    // In header: <boost/signals2/optional_last_value.hpp>

    class optional_last_value<void> {
    public:
      // types
      typedef void result_type;

      // invocation
      template<typename InputIterator>
        result_type operator()(InputIterator, InputIterator) const;
    };

## Description

This specialization of signals2::optional_last_value is provided to cope with the fact that there is no such thing as an `optional<void>`, which optional_last_value would otherwise try to use as its `result_type`. This specialization instead sets the `result_type` to be `void`.

### `optional_last_value` invocation

1.     template<typename InputIterator>
         result_type operator()(InputIterator first, InputIterator last) const;

   Effects: | Attempts to dereference every iterator in the sequence `[first, last)`.