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1 //===- iterator_range.h - A range adaptor for iterators ---------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 /// This provides a very simple, boring adaptor for a begin and end iterator
11 /// into a range type. This should be used to build range views that work well
12 /// with range based for loops and range based constructors.
13 ///
14 /// Note that code here follows more standards-based coding conventions as it
15 /// is mirroring proposed interfaces for standardization.
16 ///
17 //===----------------------------------------------------------------------===//
18 
19 #ifndef LLVM_ADT_ITERATOR_RANGE_H
20 #define LLVM_ADT_ITERATOR_RANGE_H
21 
22 #include <utility>
23 #include <iterator>
24 
25 namespace llvm {
26 
27 /// \brief A range adaptor for a pair of iterators.
28 ///
29 /// This just wraps two iterators into a range-compatible interface. Nothing
30 /// fancy at all.
31 template <typename IteratorT>
32 class iterator_range {
33   IteratorT begin_iterator, end_iterator;
34 
35 public:
36   //TODO: Add SFINAE to test that the Container's iterators match the range's
37   //      iterators.
38   template <typename Container>
iterator_range(Container && c)39   iterator_range(Container &&c)
40   //TODO: Consider ADL/non-member begin/end calls.
41       : begin_iterator(c.begin()), end_iterator(c.end()) {}
iterator_range(IteratorT begin_iterator,IteratorT end_iterator)42   iterator_range(IteratorT begin_iterator, IteratorT end_iterator)
43       : begin_iterator(std::move(begin_iterator)),
44         end_iterator(std::move(end_iterator)) {}
45 
begin()46   IteratorT begin() const { return begin_iterator; }
end()47   IteratorT end() const { return end_iterator; }
48 };
49 
50 /// \brief Convenience function for iterating over sub-ranges.
51 ///
52 /// This provides a bit of syntactic sugar to make using sub-ranges
53 /// in for loops a bit easier. Analogous to std::make_pair().
make_range(T x,T y)54 template <class T> iterator_range<T> make_range(T x, T y) {
55   return iterator_range<T>(std::move(x), std::move(y));
56 }
57 
make_range(std::pair<T,T> p)58 template <typename T> iterator_range<T> make_range(std::pair<T, T> p) {
59   return iterator_range<T>(std::move(p.first), std::move(p.second));
60 }
61 
62 template<typename T>
drop_begin(T && t,int n)63 iterator_range<decltype(begin(std::declval<T>()))> drop_begin(T &&t, int n) {
64   return make_range(std::next(begin(t), n), end(t));
65 }
66 }
67 
68 #endif
69