1 //===-- llvm/ADT/SetOperations.h - Generic Set Operations -------*- 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 ///
9 /// \file
10 /// This file defines generic set operations that may be used on set's of
11 /// different types, and different element types.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_ADT_SETOPERATIONS_H
16 #define LLVM_ADT_SETOPERATIONS_H
17 
18 namespace llvm {
19 
20 /// set_union(A, B) - Compute A := A u B, return whether A changed.
21 ///
22 template <class S1Ty, class S2Ty>
23 bool set_union(S1Ty &S1, const S2Ty &S2) {
24   bool Changed = false;
25 
26   for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
27        SI != SE; ++SI)
28     if (S1.insert(*SI).second)
29       Changed = true;
30 
31   return Changed;
32 }
33 
34 /// set_intersect(A, B) - Compute A := A ^ B
35 /// Identical to set_intersection, except that it works on set<>'s and
36 /// is nicer to use.  Functionally, this iterates through S1, removing
37 /// elements that are not contained in S2.
38 ///
39 template <class S1Ty, class S2Ty>
40 void set_intersect(S1Ty &S1, const S2Ty &S2) {
41    for (typename S1Ty::iterator I = S1.begin(); I != S1.end();) {
42      const auto &E = *I;
43      ++I;
44      if (!S2.count(E)) S1.erase(E);   // Erase element if not in S2
45    }
46 }
47 
48 /// set_difference(A, B) - Return A - B
49 ///
50 template <class S1Ty, class S2Ty>
51 S1Ty set_difference(const S1Ty &S1, const S2Ty &S2) {
52   S1Ty Result;
53   for (typename S1Ty::const_iterator SI = S1.begin(), SE = S1.end();
54        SI != SE; ++SI)
55     if (!S2.count(*SI))       // if the element is not in set2
56       Result.insert(*SI);
57   return Result;
58 }
59 
60 /// set_subtract(A, B) - Compute A := A - B
61 ///
62 template <class S1Ty, class S2Ty>
63 void set_subtract(S1Ty &S1, const S2Ty &S2) {
64   for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
65        SI != SE; ++SI)
66     S1.erase(*SI);
67 }
68 
69 /// set_is_subset(A, B) - Return true iff A in B
70 ///
71 template <class S1Ty, class S2Ty>
72 bool set_is_subset(const S1Ty &S1, const S2Ty &S2) {
73   if (S1.size() > S2.size())
74     return false;
75   for (const auto It : S1)
76     if (!S2.count(It))
77       return false;
78   return true;
79 }
80 
81 } // End llvm namespace
82 
83 #endif
84