setdiff function like matlab

Former-commit-id: 6ba5c353ca0a71f03c807782e7ce6acdd56c4ea5

include/igl/setdiff.cpp

@@ -0,0 +1,83 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2014 Alec Jacobson <alecjacobson@gmail.com>
+// 
+// This Source Code Form is subject to the terms of the Mozilla Public License 
+// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
+// obtain one at http://mozilla.org/MPL/2.0/.
+#include "setdiff.h"
+#include "colon.h"
+#include "list_to_matrix.h"
+#include "sort.h"
+#include "unique.h"
+
+template <
+  typename DerivedA,
+  typename DerivedB,
+  typename DerivedC,
+  typename DerivedIA>
+IGL_INLINE void igl::setdiff(
+  const Eigen::PlainObjectBase<DerivedA> & A,
+  const Eigen::PlainObjectBase<DerivedB> & B,
+  Eigen::PlainObjectBase<DerivedC> & C,
+  Eigen::PlainObjectBase<DerivedIA> & IA)
+{
+  using namespace Eigen;
+  using namespace std;
+  // boring base cases
+  if(A.size() == 0)
+  {
+    C.resize(0,1);
+    IA.resize(0,1);
+  }
+  if(B.size() == 0)
+  {
+    C.resize(A.size(),1);
+    copy(A.data(),A.data()+A.size(),C.data());
+    IA = igl::colon<typename DerivedIA::Scalar>(0,C.size()-1);
+  }
+
+  // Get rid of any duplicates
+  typedef Matrix<typename DerivedA::Scalar,Dynamic,1> VectorA;
+  typedef Matrix<typename DerivedB::Scalar,Dynamic,1> VectorB;
+  VectorA uA;
+  VectorB uB;
+  typedef PlainObjectBase<DerivedIA> IAType;
+  IAType uIA,uIuA,uIB,uIuB;
+  unique(A,uA,uIA,uIuA);
+  unique(B,uB,uIB,uIuB);
+
+  // Sort both
+  VectorA sA;
+  VectorB sB;
+  IAType sIA,sIB;
+  sort(uA,1,true,sA,sIA);
+  sort(uB,1,true,sB,sIB);
+
+  vector<typename DerivedB::Scalar> vC;
+  vector<typename DerivedIA::Scalar> vIA;
+  int bi = 0;
+  // loop over sA
+  bool past = false;
+  for(int a = 0;a<sA.size();a++)
+  {
+    while(!past && sA(a)>sB(bi))
+    {
+      bi++;
+      past = bi>=sB.size();
+    }
+    if(past || sA(a)<sB(bi))
+    {
+      // then sA(a) did not appear in sB
+      vC.push_back(sA(a));
+      vIA.push_back(uIA(sIA(a)));
+    }
+  }
+  list_to_matrix(vC,C);
+  list_to_matrix(vIA,IA);
+}
+
+#ifndef IGL_HEADER_ONLY
+// Explicit template specialization
+template void igl::setdiff<Eigen::Matrix<int, -1, 1, 0, -1, 1>, Eigen::Matrix<int, -1, 1, 0, -1, 1>, Eigen::Matrix<int, -1, 1, 0, -1, 1>, Eigen::Matrix<int, -1, 1, 0, -1, 1> >(Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> >&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> >&);
+#endif

include/igl/setdiff.h

@@ -0,0 +1,38 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2014 Alec Jacobson <alecjacobson@gmail.com>
+// 
+// This Source Code Form is subject to the terms of the Mozilla Public License 
+// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
+// obtain one at http://mozilla.org/MPL/2.0/.
+#ifndef IGL_SETDIFF_H
+#define IGL_SETDIFF_H
+#include "igl_inline.h"
+#include <Eigen/Core>
+namespace igl
+{
+  // Set difference of elements of matrices
+  //
+  // Inputs:
+  //   A  m-long vector of indices
+  //   B  n-long vector of indices
+  // Outputs:
+  //   C  (k<=m)-long vector of unique elements appearing in A but not in B
+  //   IA  (k<=m)-long list of indices into A so that C = A(IA)
+  //
+  template <
+    typename DerivedA,
+    typename DerivedB,
+    typename DerivedC,
+    typename DerivedIA>
+  IGL_INLINE void setdiff(
+    const Eigen::PlainObjectBase<DerivedA> & A,
+    const Eigen::PlainObjectBase<DerivedB> & B,
+    Eigen::PlainObjectBase<DerivedC> & C,
+    Eigen::PlainObjectBase<DerivedIA> & IA);
+}
+
+#ifdef IGL_HEADER_ONLY
+#  include "setdiff.cpp"
+#endif
+#endif