/* nag_lambertW (c05bac) Example Program.
 *
 * Copyright 2008, Numerical Algorithms Group.
 *
 * Mark 9, 2009.
 */

#include <stdio.h>
#include <math.h>
#include <nag.h>
#include <nagx04.h>
#include <nag_stdlib.h>
#include <nagc05.h>

int main(int argc, char *argv[])
{
  FILE        *fpin, *fpout;
  /* Scalars */
  double      w, x;
  Integer     branch;
  Integer     exit_status = 0;
  char        offset[10];
  Nag_Boolean offsetenum;
  NagError    fail;

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpin = nag_example_file_io(argc, argv, "-data", NULL);
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fprintf(fpout, "nag_lambertW (c05bac) Example Program Results\n");
  /* Skip heading in data file*/
  fscanf(fpin, "%*[^\n] ");
  fscanf(fpin, "%ld%*[^\n] ", &branch);
  fscanf(fpin, "%s%*[^\n] ", offset);
  /*
   * nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  offsetenum = (Nag_Boolean) nag_enum_name_to_value(offset);
  fprintf(fpout, "\n");
  fprintf(fpout, "branch = %ld\n", branch);
  fprintf(fpout, "offset = %s\n", offset);
  fprintf(fpout, "\n      x           w(x)\n\n");
  while (fscanf(fpin, "%lf%*[^\n] ", &x) != EOF)
    {
      /*
       * nag_lambertW (c05bac)
       * Real values of Lambert's W function, W(x)
       */
      w = nag_lambertW(x, branch, offsetenum, &fail);
      if (fail.code == NE_NOERROR)
        {
          fprintf(fpout, "%14.5e%14.5e\n", x, w);
        }
      else
        {
          fprintf(fpout, "Error from nag_lambertW (c05bac).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }
    }

 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  return exit_status;
}