IteratorX.h

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/**********************************************************************
 
 Audacity: A Digital Audio Editor
 
 @file IteratorX.h
 
 C++ standard header <iterator> with a few extensions
 
 Paul Licameli split from MemoryX.h
 
 **********************************************************************/
#ifndef __AUDACITY_ITERATOR_X__
#define __AUDACITY_ITERATOR_X__
 
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
 
template< typename Value, typename Category = std::forward_iterator_tag >
struct ValueIterator{
   using iterator_category = Category;
   using value_type = Value;
   using difference_type = ptrdiff_t;
   // void pointer type so that operator -> is disabled
   using pointer = void;
   // make "reference type" really the same as the value type
   using reference = const Value;
};
 
template <typename Iterator>
struct IteratorRange : public std::pair<Iterator, Iterator> {
   using iterator = Iterator;
   using reverse_iterator = std::reverse_iterator<Iterator>;
 
   IteratorRange (const Iterator &a, const Iterator &b)
   : std::pair<Iterator, Iterator> ( a, b ) {}
 
   IteratorRange (Iterator &&a, Iterator &&b)
   : std::pair<Iterator, Iterator> ( std::move(a), std::move(b) ) {}
 
   IteratorRange< reverse_iterator > reversal () const
   { return { this->rbegin(), this->rend() }; }
 
   Iterator begin() const { return this->first; }
   Iterator end() const { return this->second; }
 
   reverse_iterator rbegin() const { return reverse_iterator{ this->second }; }
   reverse_iterator rend() const { return reverse_iterator{ this->first }; }
 
   bool empty() const { return this->begin() == this->end(); }
   explicit operator bool () const { return !this->empty(); }
   size_t size() const { return std::distance(this->begin(), this->end()); }
 
   template <typename T> iterator find(const T &t) const
   { return std::find(this->begin(), this->end(), t); }
 
   template <typename T> long index(const T &t) const
   {
      auto iter = this->find(t);
      if (iter == this->end())
         return -1;
      return std::distance(this->begin(), iter);
   }
 
   template <typename T> bool contains(const T &t) const
   { return this->end() != this->find(t); }
 
   template <typename F> iterator find_if(const F &f) const
   { return std::find_if(this->begin(), this->end(), f); }
 
   template <typename F> long index_if(const F &f) const
   {
      auto iter = this->find_if(f);
      if (iter == this->end())
         return -1;
      return std::distance(this->begin(), iter);
   }
 
   // to do: use std::all_of, any_of, none_of when available on all platforms
   template <typename F> bool all_of(const F &f) const
   {
      auto notF =
         [&](typename std::iterator_traits<Iterator>::reference v)
            { return !f(v); };
      return !this->any_of( notF );
   }
 
   template <typename F> bool any_of(const F &f) const
   { return this->end() != this->find_if(f); }
 
   template <typename F> bool none_of(const F &f) const
   { return !this->any_of(f); }
 
   template<typename T> struct identity
      { const T&& operator () (T &&v) const { return std::forward(v); } };
 
   // Like std::accumulate, but the iterators implied, and with another
   // unary operation on the iterator value, pre-composed
   template<
      typename R,
      typename Binary = std::plus< R >,
      typename Unary = identity< decltype( *std::declval<Iterator>() ) >
   >
   R accumulate(
      R init,
      Binary binary_op = {},
      Unary unary_op = {}
   ) const
   {
      R result = init;
      for (auto&& v : *this)
         result = binary_op(result, unary_op(v));
      return result;
   }
 
   // An overload making it more convenient to use with pointers to member
   // functions
   template<
      typename R,
      typename Binary = std::plus< R >,
      typename R2, typename C
   >
   R accumulate(
      R init,
      Binary binary_op,
      R2 (C :: * pmf) () const
   ) const
   {
      return this->accumulate( init, binary_op, std::mem_fn( pmf ) );
   }
 
   // Some accumulations frequent enough to be worth abbreviation:
   template<
      typename Unary = identity< decltype( *std::declval<Iterator>() ) >,
      typename R = decltype( std::declval<Unary>()( *std::declval<Iterator>() ) )
   >
   R min( Unary unary_op = {} ) const
   {
      return this->accumulate(
         std::numeric_limits< R >::max(),
         (const R&(*)(const R&, const R&)) std::min,
         unary_op
      );
   }
 
   template<
      typename R2, typename C,
      typename R = R2
   >
   R min( R2 (C :: * pmf) () const ) const
   {
      return this->min( std::mem_fn( pmf ) );
   }
 
   template<
      typename Unary = identity< decltype( *std::declval<Iterator>() ) >,
      typename R = decltype( std::declval<Unary>()( *std::declval<Iterator>() ) )
   >
   R max( Unary unary_op = {} ) const
   {
      return this->accumulate(
         std::numeric_limits< R >::lowest(),
         (const R&(*)(const R&, const R&)) std::max,
         unary_op
      );
   }
 
   template<
      typename R2, typename C,
      typename R = R2
   >
   R max( R2 (C :: * pmf) () const ) const
   {
      return this->max( std::mem_fn( pmf ) );
   }
 
   template<
      typename Unary = identity< decltype( *std::declval<Iterator>() ) >,
      typename R = decltype( std::declval<Unary>()( *std::declval<Iterator>() ) )
   >
   R sum( Unary unary_op = {} ) const
   {
      return this->accumulate(
         R{ 0 },
         std::plus< R >{},
         unary_op
      );
   }
 
   template<
      typename R2, typename C,
      typename R = R2
   >
   R sum( R2 (C :: * pmf) () const ) const
   {
      return this->sum( std::mem_fn( pmf ) );
   }
};
 
template< typename Iterator>
IteratorRange< Iterator >
make_iterator_range( const Iterator &i1, const Iterator &i2 )
{
   return { i1, i2 };
}
 
template< typename Container >
IteratorRange< typename Container::iterator >
make_iterator_range( Container &container )
{
   return { container.begin(), container.end() };
}
 
template< typename Container >
IteratorRange< typename Container::const_iterator >
make_iterator_range( const Container &container )
{
   return { container.begin(), container.end() };
}
 
// A utility function building a container of results
template< typename Container, typename Iterator, typename Function >
Container transform_range( Iterator first, Iterator last, Function &&fn )
{
   Container result;
   std::transform( first, last, std::back_inserter( result ), fn );
   return result;
}
// A utility function, often constructing a vector from another vector
template< typename OutContainer, typename InContainer, typename Function >
OutContainer transform_container( InContainer &inContainer, Function &&fn )
{
   return transform_range<OutContainer>(
      inContainer.begin(), inContainer.end(), fn );
}
 
template<typename Range, typename Function>
void for_each_in_range(Range &&range, Function &&fn)
{
   std::for_each(range.begin(), range.end(), std::forward<Function>(fn));
}
 
template<typename Integral = int>
class NumberIterator : public ValueIterator<Integral>
{
public:
   explicit NumberIterator(Integral value) : mValue{ value } {}
 
   Integral operator *() const { return mValue; }
   NumberIterator &operator ++() { ++mValue; return *this; }
   NumberIterator operator ++(int) const
   { auto result = *this; ++result; return result; }
 
   friend bool operator ==(NumberIterator x, NumberIterator y)
   { return x.mValue == y.mValue; }
   friend bool operator !=(NumberIterator x, NumberIterator y)
   { return !(x == y); }
 
private:
   Integral mValue;
};
 
template<typename Integral> struct IotaRange
   : IteratorRange<NumberIterator<Integral>>
{
   IotaRange(Integral inclusiveLower, Integral exclusiveUpper)
      : IteratorRange<NumberIterator<Integral>>{
         NumberIterator{ inclusiveLower }, NumberIterator{ exclusiveUpper } }
   {}
};
 
#endif // __AUDACITY_MEMORY_X_H__