text: /* -*- mode: C -*-  */
  /* 
     IGraph library.
     Copyright (C) 2006-2012  Gabor Csardi <csardi.gabor@gmail.com>
     334 Harvard st, Cambridge MA, 02139 USA
     
     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 2 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, write to the Free Software
     Foundation, Inc.,  51 Franklin Street, Fifth Floor, Boston, MA 
     02110-1301 USA
  
  */
  
  #include <igraph.h>
  
  int main() {
    
    igraph_t g;
    igraph_real_t res;
  
    /* Trivial cases */
  
    igraph_ring(&g, 100, IGRAPH_UNDIRECTED, 0, 0);
    igraph_transitivity_undirected(&g, &res, IGRAPH_TRANSITIVITY_NAN);
    igraph_destroy(&g);
  
    if (res != 0) {
      return 1;
    }
  
    igraph_full(&g, 20, IGRAPH_UNDIRECTED, IGRAPH_NO_LOOPS);
    igraph_transitivity_undirected(&g, &res, IGRAPH_TRANSITIVITY_NAN);
    igraph_destroy(&g);
    
    if (res != 1) {
      return 2;
    }
  
    /* Degenerate cases */
    igraph_small(&g, 0, IGRAPH_UNDIRECTED,
  		  0,  1,  2,  3,  4,  5, -1);
    igraph_transitivity_undirected(&g, &res, IGRAPH_TRANSITIVITY_NAN);
    /* res should be NaN here, any comparison must return false */
    if (res == 0 || res > 0 || res < 0) {
  	return 4;
    }
    igraph_transitivity_undirected(&g, &res, IGRAPH_TRANSITIVITY_ZERO);
    /* res should be zero here */
    if (res) {
  	return 5;
    }
    igraph_destroy(&g);
  
    /* Zachary Karate club */
  
    igraph_small(&g, 0, IGRAPH_UNDIRECTED, 
  	       0,  1,  0,  2,  0,  3,  0,  4,  0,  5,
  	       0,  6,  0,  7,  0,  8,  0, 10,  0, 11,
  	       0, 12,  0, 13,  0, 17,  0, 19,  0, 21,
  	       0, 31,  1,  2,  1,  3,  1,  7,  1, 13,
  	       1, 17,  1, 19,  1, 21,  1, 30,  2,  3,
  	       2,  7,  2,  8,  2,  9,  2, 13,  2, 27,
  	       2, 28,  2, 32,  3,  7,  3, 12,  3, 13,
  	       4,  6,  4, 10,  5,  6,  5, 10,  5, 16,
  	       6, 16,  8, 30,  8, 32,  8, 33,  9, 33,
  	       13, 33, 14, 32, 14, 33, 15, 32, 15, 33,
  	       18, 32, 18, 33, 19, 33, 20, 32, 20, 33,
  	       22, 32, 22, 33, 23, 25, 23, 27, 23, 29,
  	       23, 32, 23, 33, 24, 25, 24, 27, 24, 31,
  	       25, 31, 26, 29, 26, 33, 27, 33, 28, 31,
  	       28, 33, 29, 32, 29, 33, 30, 32, 30, 33,
  	       31, 32, 31, 33, 32, 33,
  	       -1);  
    
    igraph_transitivity_undirected(&g, &res, IGRAPH_TRANSITIVITY_NAN);
    igraph_destroy(&g);
    
    if (res != 0.2556818181818181767717) {
      fprintf(stderr, "%f != %f\n", res, 0.2556818181818181767717);
      return 3;
    }
  
    return 0;
  }
  