include/llvm/ADT/iterator_range.h

   1 //===- iterator_range.h - A range adaptor for iterators ---------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 /// \file
   9 /// This provides a very simple, boring adaptor for a begin and end iterator
  10 /// into a range type. This should be used to build range views that work well
  11 /// with range based for loops and range based constructors.
  12 ///
  13 /// Note that code here follows more standards-based coding conventions as it
  14 /// is mirroring proposed interfaces for standardization.
  15 ///
  16 //===----------------------------------------------------------------------===//
  17
  18 #ifndef LLVM_ADT_ITERATOR_RANGE_H
  19 #define LLVM_ADT_ITERATOR_RANGE_H
  20
  21 #include <iterator>
  22 #include <utility>
  23
  24 namespace llvm {
  25
  26 /// A range adaptor for a pair of iterators.
  27 ///
  28 /// This just wraps two iterators into a range-compatible interface. Nothing
  29 /// fancy at all.
  30 template <typename IteratorT>
  31 class iterator_range {
  32   IteratorT begin_iterator, end_iterator;
  33
  34 public:
  35   //TODO: Add SFINAE to test that the Container's iterators match the range's
  36   //      iterators.
  37   template <typename Container>
  38   iterator_range(Container &&c)
  39   //TODO: Consider ADL/non-member begin/end calls.
  40       : begin_iterator(c.begin()), end_iterator(c.end()) {}
  41   iterator_range(IteratorT begin_iterator, IteratorT end_iterator)
  42       : begin_iterator(std::move(begin_iterator)),
  43         end_iterator(std::move(end_iterator)) {}
  44
  45   IteratorT begin() const { return begin_iterator; }
  46   IteratorT end() const { return end_iterator; }
  47   bool empty() const { return begin_iterator == end_iterator; }
  48 };
  49
  50 /// 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().
  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
  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>
  63 iterator_range<decltype(adl_begin(std::declval<T>()))> drop_begin(T &&t,
  64                                                                   int n) {
  65   return make_range(std::next(adl_begin(t), n), adl_end(t));
  66 }
  67 }
  68
  69 #endif