Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/libigl/igl/avg_edge_length.h

@@ -0,0 +1,41 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2013 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_AVERAGEEDGELENGTH_H
+#define IGL_AVERAGEEDGELENGTH_H
+
+#include "igl_inline.h"
+#include <Eigen/Core>
+#include <string>
+#include <vector>
+
+namespace igl 
+{
+  // Compute the average edge length for the given triangle mesh
+  // Templates:
+  //   DerivedV derived from vertex positions matrix type: i.e. MatrixXd
+  //   DerivedF derived from face indices matrix type: i.e. MatrixXi
+  //   DerivedL derived from edge lengths matrix type: i.e. MatrixXd
+  // Inputs:
+  //   V  eigen matrix #V by 3
+  //   F  #F by simplex-size list of mesh faces (must be simplex)
+  // Outputs:
+  //   l  average edge length
+  //
+  // See also: adjacency_matrix
+  template <typename DerivedV, typename DerivedF>
+  IGL_INLINE double avg_edge_length(
+    const Eigen::MatrixBase<DerivedV>& V,
+    const Eigen::MatrixBase<DerivedF>& F);
+
+}
+
+#ifndef IGL_STATIC_LIBRARY
+#  include "avg_edge_length.cpp"
+#endif
+
+#endif