1 files changed, 84 insertions, 0 deletions
diff --git a/src/Coxeter_triangulation/include/gudhi/Functions/Negation.h b/src/Coxeter_triangulation/include/gudhi/Functions/Negation.h
new file mode 100644
index 00000000..fdf07f27
--- /dev/null
+++ b/src/Coxeter_triangulation/include/gudhi/Functions/Negation.h
@@ -0,0 +1,84 @@
+/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
+ *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
+ *    Author(s):       Siargey Kachanovich
+ *
+ *    Copyright (C) 2019 Inria
+ *
+ *    Modification(s):
+ *      - YYYY/MM Author: Description of the modification
+ */
+
+#ifndef FUNCTIONS_NEGATION_H_
+#define FUNCTIONS_NEGATION_H_
+
+#include <cstdlib>  // for std::size_t
+
+#include <Eigen/Dense>
+
+namespace Gudhi {
+
+namespace coxeter_triangulation {
+
+/**
+ *\class Negation
+ * \brief Constructs the "minus" function. The zero-set is the same, but
+ * the values at other points are the negative of their original value.
+ *
+ * \tparam Function_ The function template parameter. Should be a model of
+ * the concept FunctionForImplicitManifold.
+ */
+template <class Function_>
+struct Negation {
+  /**
+   * \brief Value of the function at a specified point.
+   * @param[in] p The input point. The dimension needs to coincide with the ambient dimension.
+   */
+  Eigen::VectorXd operator()(const Eigen::VectorXd& p) const {
+    Eigen::VectorXd result = -fun_(p);
+    return result;
+  }
+
+  /** \brief Returns the domain (ambient) dimension. */
+  std::size_t amb_d() const { return fun_.amb_d(); }
+
+  /** \brief Returns the codomain dimension. */
+  std::size_t cod_d() const { return fun_.cod_d(); }
+
+  /** \brief Returns a point on the zero-set. */
+  Eigen::VectorXd seed() const {
+    Eigen::VectorXd result = fun_.seed();
+    return result;
+  }
+
+  /**
+   * \brief Constructor of the negative function.
+   *
+   * @param[in] function The function to be negated.
+   */
+  Negation(const Function_& function) : fun_(function) {}
+
+ private:
+  Function_ fun_;
+};
+
+/**
+ * \brief Static constructor of the negative function.
+ *
+ * @param[in] function The function to be translated.
+ * domain (ambient) dimension of 'function'.
+ *
+ * \tparam Function_ The function template parameter. Should be a model of
+ * the concept FunctionForImplicitManifold.
+ *
+ * \ingroup coxeter_triangulation
+ */
+template <class Function_>
+Negation<Function_> negation(const Function_& function) {
+  return Negation<Function_>(function);
+}
+
+}  // namespace coxeter_triangulation
+
+}  // namespace Gudhi
+
+#endif