llvm-mirror/include/llvm/ADT/STLExtras.h

//===- llvm/ADT/STLExtras.h - Useful STL related functions ------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains some templates that are useful if you are working with the
// STL at all.
//
// No library is required when using these functinons.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_STLEXTRAS_H
#define LLVM_ADT_STLEXTRAS_H

#include <functional>
#include <utility> // for std::pair
#include "llvm/ADT/iterator"

namespace llvm {

//===----------------------------------------------------------------------===//
//     Extra additions to <functional>
//===----------------------------------------------------------------------===//

template<class Ty>
struct greater_ptr : public std::binary_function<Ty, Ty, bool> {
  bool operator()(const Ty* left, const Ty* right) const {
    return *right < *left;
  }
};

// deleter - Very very very simple method that is used to invoke operator
// delete on something.  It is used like this:
//
//   for_each(V.begin(), B.end(), deleter<Interval>);
//
template <class T>
static inline void deleter(T *Ptr) {
  delete Ptr;
}



//===----------------------------------------------------------------------===//
//     Extra additions to <iterator>
//===----------------------------------------------------------------------===//

// mapped_iterator - This is a simple iterator adapter that causes a function to
// be dereferenced whenever operator* is invoked on the iterator.
//
template <class RootIt, class UnaryFunc>
class mapped_iterator {
  RootIt current;
  UnaryFunc Fn;
public:
  typedef typename std::iterator_traits<RootIt>::iterator_category
          iterator_category;
  typedef typename std::iterator_traits<RootIt>::difference_type
          difference_type;
  typedef typename UnaryFunc::result_type value_type;

  typedef void pointer;
  //typedef typename UnaryFunc::result_type *pointer;
  typedef void reference;        // Can't modify value returned by fn

  typedef RootIt iterator_type;
  typedef mapped_iterator<RootIt, UnaryFunc> _Self;

  inline RootIt &getCurrent() const { return current; }

  inline explicit mapped_iterator(const RootIt &I, UnaryFunc F)
    : current(I), Fn(F) {}
  inline mapped_iterator(const mapped_iterator &It)
    : current(It.current), Fn(It.Fn) {}

  inline value_type operator*() const {   // All this work to do this
    return Fn(*current);         // little change
  }

  _Self& operator++() { ++current; return *this; }
  _Self& operator--() { --current; return *this; }
  _Self  operator++(int) { _Self __tmp = *this; ++current; return __tmp; }
  _Self  operator--(int) { _Self __tmp = *this; --current; return __tmp; }
  _Self  operator+    (difference_type n) const { return _Self(current + n); }
  _Self& operator+=   (difference_type n) { current += n; return *this; }
  _Self  operator-    (difference_type n) const { return _Self(current - n); }
  _Self& operator-=   (difference_type n) { current -= n; return *this; }
  reference operator[](difference_type n) const { return *(*this + n); }

  inline bool operator!=(const _Self &X) const { return !operator==(X); }
  inline bool operator==(const _Self &X) const { return current == X.current; }
  inline bool operator< (const _Self &X) const { return current <  X.current; }

  inline difference_type operator-(const _Self &X) const {
    return current - X.current;
  }
};

template <class _Iterator, class Func>
inline mapped_iterator<_Iterator, Func>
operator+(typename mapped_iterator<_Iterator, Func>::difference_type N,
          const mapped_iterator<_Iterator, Func>& X) {
  return mapped_iterator<_Iterator, Func>(X.getCurrent() - N);
}


// map_iterator - Provide a convenient way to create mapped_iterators, just like
// make_pair is useful for creating pairs...
//
template <class ItTy, class FuncTy>
inline mapped_iterator<ItTy, FuncTy> map_iterator(const ItTy &I, FuncTy F) {
  return mapped_iterator<ItTy, FuncTy>(I, F);
}


// next/prior - These functions unlike std::advance do not modify the
// passed iterator but return a copy.
//
// next(myIt) returns copy of myIt incremented once
// next(myIt, n) returns copy of myIt incremented n times
// prior(myIt) returns copy of myIt decremented once
// prior(myIt, n) returns copy of myIt decremented n times

template <typename ItTy, typename Dist>
inline ItTy next(ItTy it, Dist n)
{
  std::advance(it, n);
  return it;
}

template <typename ItTy>
inline ItTy next(ItTy it)
{
  std::advance(it, 1);
  return it;
}

template <typename ItTy, typename Dist>
inline ItTy prior(ItTy it, Dist n)
{
  std::advance(it, -n);
  return it;
}

template <typename ItTy>
inline ItTy prior(ItTy it)
{
  std::advance(it, -1);
  return it;
}

//===----------------------------------------------------------------------===//
//     Extra additions to <utility>
//===----------------------------------------------------------------------===//

// tie - this function ties two objects and returns a temporary object
// that is assignable from a std::pair. This can be used to make code
// more readable when using values returned from functions bundled in
// a std::pair. Since an example is worth 1000 words:
//
// typedef std::map<int, int> Int2IntMap;
//
// Int2IntMap myMap;
// Int2IntMap::iterator where;
// bool inserted;
// tie(where, inserted) = myMap.insert(std::make_pair(123,456));
//
// if (inserted)
//   // do stuff
// else
//   // do other stuff

namespace
{
  template <typename T1, typename T2>
  struct tier {
    typedef T1 &first_type;
    typedef T2 &second_type;

    first_type first;
    second_type second;

    tier(first_type f, second_type s) : first(f), second(s) { }
    tier& operator=(const std::pair<T1, T2>& p) {
      first = p.first;
      second = p.second;
      return *this;
    }
  };
}

template <typename T1, typename T2>
inline tier<T1, T2> tie(T1& f, T2& s) {
  return tier<T1, T2>(f, s);
}

} // End llvm namespace

#endif