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      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 // This file defines generic set operations that may be used on set's of
     10 // different types, and different element types.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_ADT_SETOPERATIONS_H
     15 #define LLVM_ADT_SETOPERATIONS_H
     16 
     17 namespace llvm {
     18 
     19 /// set_union(A, B) - Compute A := A u B, return whether A changed.
     20 ///
     21 template <class S1Ty, class S2Ty>
     22 bool set_union(S1Ty &S1, const S2Ty &S2) {
     23   bool Changed = false;
     24 
     25   for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
     26        SI != SE; ++SI)
     27     if (S1.insert(*SI).second)
     28       Changed = true;
     29 
     30   return Changed;
     31 }
     32 
     33 /// set_intersect(A, B) - Compute A := A ^ B
     34 /// Identical to set_intersection, except that it works on set<>'s and
     35 /// is nicer to use.  Functionally, this iterates through S1, removing
     36 /// elements that are not contained in S2.
     37 ///
     38 template <class S1Ty, class S2Ty>
     39 void set_intersect(S1Ty &S1, const S2Ty &S2) {
     40    for (typename S1Ty::iterator I = S1.begin(); I != S1.end();) {
     41      const auto &E = *I;
     42      ++I;
     43      if (!S2.count(E)) S1.erase(E);   // Erase element if not in S2
     44    }
     45 }
     46 
     47 /// set_difference(A, B) - Return A - B
     48 ///
     49 template <class S1Ty, class S2Ty>
     50 S1Ty set_difference(const S1Ty &S1, const S2Ty &S2) {
     51   S1Ty Result;
     52   for (typename S1Ty::const_iterator SI = S1.begin(), SE = S1.end();
     53        SI != SE; ++SI)
     54     if (!S2.count(*SI))       // if the element is not in set2
     55       Result.insert(*SI);
     56   return Result;
     57 }
     58 
     59 /// set_subtract(A, B) - Compute A := A - B
     60 ///
     61 template <class S1Ty, class S2Ty>
     62 void set_subtract(S1Ty &S1, const S2Ty &S2) {
     63   for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
     64        SI != SE; ++SI)
     65     S1.erase(*SI);
     66 }
     67 
     68 /// set_is_subset(A, B) - Return true iff A in B
     69 ///
     70 template <class S1Ty, class S2Ty>
     71 bool set_is_subset(const S1Ty &S1, const S2Ty &S2) {
     72   if (S1.size() > S2.size())
     73     return false;
     74   for (const auto It : S1)
     75     if (!S2.count(It))
     76       return false;
     77   return true;
     78 }
     79 
     80 /// set_is_strict_subset(A, B) - Return true iff A in B and and A != B
     81 ///
     82 template <class S1Ty, class S2Ty>
     83 bool set_is_strict_subset(const S1Ty &S1, const S2Ty &S2) {
     84   if (S1.size() >= S2.size())
     85     return false;
     86   return set_is_subset(S1, S2);
     87 }
     88 
     89 } // End llvm namespace
     90 
     91 #endif
     92