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diff --git a/src/Persistent_cohomology/include/gudhi/Persistent_cohomology/Field_Zp.h b/src/Persistent_cohomology/include/gudhi/Persistent_cohomology/Field_Zp.h
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+ /*    This file is part of the Gudhi Library. The Gudhi library 
+  *    (Geometric Understanding in Higher Dimensions) is a generic C++ 
+  *    library for computational topology.
+  *
+  *    Author(s):       Clément Maria
+  *
+  *    Copyright (C) 2014  INRIA Sophia Antipolis-Méditerranée (France)
+  *
+  *    This program is free software: you can redistribute it and/or modify
+  *    it under the terms of the GNU General Public License as published by
+  *    the Free Software Foundation, either version 3 of the License, or
+  *    (at your option) any later version.
+  *
+  *    This program is distributed in the hope that it will be useful,
+  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  *    GNU General Public License for more details.
+  *
+  *    You should have received a copy of the GNU General Public License
+  *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+  */
+
+#ifndef GUDHI_FIELD_ZP_H
+#define GUDHI_FIELD_ZP_H
+
+namespace Gudhi{
+
+/** \brief Structure representing the coefficient field \f$\mathbb{Z}/p\mathbb{Z}\f$
+  *
+  * \implements CoefficientField
+  * \ingroup persistent_cohomology
+  */
+class Field_Zp {
+public:
+typedef int Element;
+
+Field_Zp()
+: Prime(-1)
+, inverse_() {}
+
+void init(int charac ) {
+  assert(charac <= 32768);
+  Prime = charac;
+  inverse_.clear();
+  inverse_.reserve(charac);
+  inverse_.push_back(0);
+  for(int i=1 ; i<Prime ; ++i)
+  { 
+    int inv = 1; 
+    while(((inv * i) % Prime) != 1) ++inv;
+    inverse_.push_back(inv); 
+  }
+}
+
+/** Set x <- x + w * y*/
+void plus_times_equal ( Element & x, Element y, Element w ) 
+{ x = (x + w * y) % Prime; }
+
+// operator= defined on Element
+
+/** Returns y * w */
+Element times ( Element y, int w ) { 
+  Element res = (y * w) % Prime;
+  if(res < 0) return res+Prime;
+  else return res; 
+}
+
+void clear_coefficient(Element x) {}
+
+void plus_equal(Element & x, Element y) { x = ((x+y)%Prime); }
+
+/** \brief Returns the additive idendity \f$0_{\Bbbk}\f$ of the field.*/
+Element additive_identity () { return 0; }
+/** \brief Returns the multiplicative identity \f$1_{\Bbbk}\f$ of the field.*/
+Element multiplicative_identity ( Element P = 0) { return 1; }
+/** Returns the inverse in the field. Modifies P.*/
+std::pair<Element,Element> inverse ( Element x
+                                   , Element P ) 
+{ return std::pair<Element,Element>(inverse_[x],P); 
+}  // <------ return the product of field characteristic for which x is invertible
+
+/** Returns -x * y.*/
+Element times_minus ( Element x, Element y ) 
+{ 
+  Element out = (-x * y) % Prime;
+  return (out < 0) ? out + Prime : out; 
+}
+
+
+bool is_one ( Element x ) { return x == 1; }
+bool is_zero ( Element x ) { return x == 0; }
+
+//bool is_null()
+
+/** \brief Returns the characteristic \f$p\f$ of the field.*/
+Element characteristic() { return Prime; }
+
+private:
+  Element Prime;
+/** Property map Element -> Element, which associate to an element its inverse in the field.*/
+  std::vector< Element > inverse_;
+};
+
+}  // namespace GUDHI
+
+#endif // GUDHI_FIELD_ZP_H