New Support file for operations on set like objects

llvm-svn: 1714

include/Support/SetOperations.h

@@ -0,0 +1,60 @@
+//===-- Support/SetOperations.h - Generic Set Operations ---------*- C++ -*--=//
+//
+// This file defines generic set operations that may be used on set's of
+// different types, and different element types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_SET_OPERATIONS_H
+#define LLVM_SUPPORT_SET_OPERATIONS_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