include/Support/SetOperations.h

//===-- Support/SetOperations.h - Generic Set Operations --------*- C++ -*-===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file defines generic set operations that may be used on set's of
// different types, and different element types.
//
//===----------------------------------------------------------------------===//

#ifndef SUPPORT_SETOPERATIONS_H
#define SUPPORT_SETOPERATIONS_H

// set_union(A, B) - Compute A := A u B, return whether A changed.
//
template <class S1Ty, class S2Ty>
bool set_union(S1Ty &S1, const S2Ty &S2) {   
  bool Changed = false;

  for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
       SI != SE; ++SI)
    if (S1.insert(*SI).second)
      Changed = true;

  return Changed;
}

// set_intersect(A, B) - Compute A := A ^ B
// Identical to set_intersection, except that it works on set<>'s and
// is nicer to use.  Functionally, this iterates through S1, removing
// elements that are not contained in S2.
//
template <template<class S1ElTy> class S1Ty, class ETy, class S2Ty>
void set_intersect(S1Ty<ETy> &S1, const S2Ty &S2) {
  for (typename S1Ty<ETy>::iterator I = S1.begin(); I != S1.end();) {
    const ETy &E = *I;
    ++I;
    if (!S2.count(E)) S1.erase(E);   // Erase element if not in S2
  }
}

// set_difference(A, B) - Return A - B
//
template <class S1Ty, class S2Ty>
S1Ty set_difference(const S1Ty &S1, const S2Ty &S2) {
  S1Ty Result;
  for (typename S1Ty::const_iterator SI = S1.begin(), SE = S1.end();
       SI != SE; ++SI)
    if (!S2.count(*SI))       // if the element is not in set2
      Result.insert(*SI);
  return Result;
}

// set_subtract(A, B) - Compute A := A - B
//
template <class S1Ty, class S2Ty>
void set_subtract(S1Ty &S1, const S2Ty &S2) { 
  for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end();
       SI != SE; ++SI)  
    S1.erase(*SI);
}

#endif