New header file defined with neeto utilities put in one place

llvm-svn: 50

include/llvm/Tools/STLExtras.h

@@ -0,0 +1,163 @@
+//===-- STLExtras.h - Useful functions when working with the STL --*- C++ -*--=//
+//
+// 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_TOOLS_STL_EXTRAS_H
+#define LLVM_TOOLS_STL_EXTRAS_H
+
+#include <functional>
+
+//===----------------------------------------------------------------------===//
+//     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.
+//
+// It turns out that this is disturbingly similar to boost::transform_iterator
+//
+#if 1
+template <class RootIt, class UnaryFunc>
+class mapped_iterator {
+  RootIt current;
+public:
+  typedef typename iterator_traits<RootIt>::iterator_category
+          iterator_category;
+  typedef typename iterator_traits<RootIt>::difference_type
+          difference_type;
+  typedef typename UnaryFunc::result_type value_type;
+  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) : current(I) {}
+  inline mapped_iterator(const mapped_iterator &It) : current(It.current) {}
+
+  inline value_type operator*() const {   // All this work to do this 
+    return UnaryFunc()(*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 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);
+}
+
+#else
+
+// This fails to work, because some iterators are not classes, for example
+// vector iterators are commonly value_type **'s
+template <class RootIt, class UnaryFunc>
+class mapped_iterator : public RootIt {
+public:
+  typedef typename UnaryFunc::result_type value_type;
+  typedef typename UnaryFunc::result_type *pointer;
+  typedef void reference;        // Can't modify value returned by fn
+
+  typedef mapped_iterator<RootIt, UnaryFunc> _Self;
+  typedef RootIt super;
+  inline explicit mapped_iterator(const RootIt &I) : super(I) {}
+  inline mapped_iterator(const super &It) : super(It) {}
+
+  inline value_type operator*() const {     // All this work to do 
+    return UnaryFunc(super::operator*());   // this little thing
+  }
+};
+#endif
+
+// 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);
+}
+
+
+
+//===----------------------------------------------------------------------===//
+//     Extra additions to <algorithm>
+//===----------------------------------------------------------------------===//
+
+// reduce - Reduce a sequence values into a single value, given an initial
+// value and an operator.
+//
+template <class InputIt, class Function, class ValueType>
+ValueType reduce(InputIt First, InputIt Last, Function Func, ValueType Value) {
+  for ( ; First != Last; ++First)
+    Value = Func(*First, Value);
+  return Value;
+}
+
+#if 1   // This is likely to be more efficient
+
+// reduce_apply - Reduce the result of applying a function to each value in a
+// sequence, given an initial value, an operator, a function, and a sequence.
+//
+template <class InputIt, class Function, class ValueType, class TransFunc>
+ValueType reduce_apply(InputIt First, InputIt Last, Function Func, 
+		       ValueType Value, TransFunc XForm) {
+  for ( ; First != Last; ++First)
+    Value = Func(XForm(*First), Value);
+  return Value;
+}
+
+#else  // This is arguably more elegant
+
+// reduce_apply - Reduce the result of applying a function to each value in a
+// sequence, given an initial value, an operator, a function, and a sequence.
+//
+template <class InputIt, class Function, class ValueType, class TransFunc>
+ValueType reduce_apply2(InputIt First, InputIt Last, Function Func, 
+		       ValueType Value, TransFunc XForm) {
+  return reduce(map_iterator(First, XForm), 
+		map_iterator(Last, XForm),
+		Func, Value);
+}
+#endif
+
+
+
+//===----------------------------------------------------------------------===//
+//     Extra additions to <functional>
+//===----------------------------------------------------------------------===//
+
+// bitwise_or - This is a simple functor that applys operator| on its two 
+// arguments to get a boolean result.
+//
+template<class Ty>
+struct bitwise_or : public binary_function<Ty, Ty, bool> {
+  bool operator()(const Ty& left, const Ty& right) const {
+    return left | right;
+  }
+};
+
+#endif