FGXMLElement.cpp

/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 Author:       Jon Berndt
 Date started: 09/28/2004
 Purpose:      XML element class
 Called by:    FGXMLParse

 ------------- Copyright (C) 2001  Jon S. Berndt (jon@jsbsim.org) -------------

 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU Lesser 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 Lesser General Public License for more
 details.

 You should have received a copy of the GNU Lesser General Public License along with
 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 Place - Suite 330, Boston, MA  02111-1307, USA.

 Further information about the GNU Lesser General Public License can also be found on
 the world wide web at http://www.gnu.org.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

#include <cmath>
#include <cstdlib>
#include <iostream>

#include "FGXMLElement.h"
#include "string_utilities.h"

using namespace std;

/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FORWARD DECLARATIONS
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

namespace JSBSim {

static const char *IdSrc = "$Id: FGXMLElement.cpp,v 1.38 2012/12/13 04:41:06 jberndt Exp $";
static const char *IdHdr = ID_XMLELEMENT;

bool Element::converterIsInitialized = false;
map <string, map <string, double> > Element::convert;

/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

Element::Element(const string& nm)
{
  name   = nm;
  parent = 0L;
  element_index = 0;

  if (!converterIsInitialized) {
    converterIsInitialized = true;
    // convert ["from"]["to"] = factor, so: from * factor = to
    // Length
    convert["M"]["FT"] = 3.2808399;
    convert["FT"]["M"] = 1.0/convert["M"]["FT"];
    convert["CM"]["FT"] = 0.032808399;
    convert["FT"]["CM"] = 1.0/convert["CM"]["FT"];
    convert["KM"]["FT"] = 3280.8399;
    convert["FT"]["KM"] = 1.0/convert["KM"]["FT"];
    convert["FT"]["IN"] = 12.0;
    convert["IN"]["FT"] = 1.0/convert["FT"]["IN"];
    convert["IN"]["M"] = convert["IN"]["FT"] * convert["FT"]["M"];
    convert["M"]["IN"] = convert["M"]["FT"] * convert["FT"]["IN"];
    // Area
    convert["M2"]["FT2"] = convert["M"]["FT"]*convert["M"]["FT"];
    convert["FT2"]["M2"] = 1.0/convert["M2"]["FT2"];
    convert["CM2"]["FT2"] = convert["CM"]["FT"]*convert["CM"]["FT"];
    convert["FT2"]["CM2"] = 1.0/convert["CM2"]["FT2"];
    convert["M2"]["IN2"] = convert["M"]["IN"]*convert["M"]["IN"];
    convert["IN2"]["M2"] = 1.0/convert["M2"]["IN2"];
    convert["FT2"]["IN2"] = 144.0;
    convert["IN2"]["FT2"] = 1.0/convert["FT2"]["IN2"];
    // Volume
    convert["IN3"]["CC"] = 16.387064;
    convert["CC"]["IN3"] = 1.0/convert["IN3"]["CC"];
    convert["FT3"]["IN3"] = 1728.0;
    convert["IN3"]["FT3"] = 1.0/convert["FT3"]["IN3"];
    convert["M3"]["FT3"] = 35.3146667;
    convert["FT3"]["M3"] = 1.0/convert["M3"]["FT3"];
    convert["LTR"]["IN3"] = 61.0237441;
    convert["IN3"]["LTR"] = 1.0/convert["LTR"]["IN3"];
    // Mass & Weight
    convert["LBS"]["KG"] = 0.45359237;
    convert["KG"]["LBS"] = 1.0/convert["LBS"]["KG"];
    convert["SLUG"]["KG"] = 14.59390;
    convert["KG"]["SLUG"] = 1.0/convert["SLUG"]["KG"];
    // Moments of Inertia
    convert["SLUG*FT2"]["KG*M2"] = 1.35594;
    convert["KG*M2"]["SLUG*FT2"] = 1.0/convert["SLUG*FT2"]["KG*M2"];
    // Angles
    convert["RAD"]["DEG"] = 180.0/M_PI;
    convert["DEG"]["RAD"] = 1.0/convert["RAD"]["DEG"];
    // Angular rates
    convert["RAD/SEC"]["DEG/SEC"] = convert["RAD"]["DEG"];
    convert["DEG/SEC"]["RAD/SEC"] = 1.0/convert["RAD/SEC"]["DEG/SEC"];
    // Spring force
    convert["LBS/FT"]["N/M"] = 14.5939;
    convert["N/M"]["LBS/FT"] = 1.0/convert["LBS/FT"]["N/M"];
    // Damping force
    convert["LBS/FT/SEC"]["N/M/SEC"] = 14.5939;
    convert["N/M/SEC"]["LBS/FT/SEC"] = 1.0/convert["LBS/FT/SEC"]["N/M/SEC"];
    // Damping force (Square Law)
    convert["LBS/FT2/SEC2"]["N/M2/SEC2"] = 47.880259;
    convert["N/M2/SEC2"]["LBS/FT2/SEC2"] = 1.0/convert["LBS/FT2/SEC2"]["N/M2/SEC2"];
    // Power
    convert["WATTS"]["HP"] = 0.001341022;
    convert["HP"]["WATTS"] = 1.0/convert["WATTS"]["HP"];
    // Force
    convert["N"]["LBS"] = 0.22482;
    convert["LBS"]["N"] = 1.0/convert["N"]["LBS"];
    // Velocity
    convert["KTS"]["FT/SEC"] = 1.68781;
    convert["FT/SEC"]["KTS"] = 1.0/convert["KTS"]["FT/SEC"];
    convert["M/S"]["FT/S"] = 3.2808399;
    convert["M/SEC"]["FT/SEC"] = 3.2808399;
    convert["FT/S"]["M/S"] = 1.0/convert["M/S"]["FT/S"];
    convert["M/SEC"]["FT/SEC"] = 3.2808399;
    convert["FT/SEC"]["M/SEC"] = 1.0/convert["M/SEC"]["FT/SEC"];
    convert["KM/SEC"]["FT/SEC"] = 3280.8399;
    convert["FT/SEC"]["KM/SEC"] = 1.0/convert["KM/SEC"]["FT/SEC"];
    // Torque
    convert["FT*LBS"]["N*M"] = 1.35581795;
    convert["N*M"]["FT*LBS"] = 1/convert["FT*LBS"]["N*M"];
    // Valve
    convert["M4*SEC/KG"]["FT4*SEC/SLUG"] = convert["M"]["FT"]*convert["M"]["FT"]*
      convert["M"]["FT"]*convert["M"]["FT"]/convert["KG"]["SLUG"];
    convert["FT4*SEC/SLUG"]["M4*SEC/KG"] =
      1.0/convert["M4*SEC/KG"]["FT4*SEC/SLUG"];
    // Pressure
    convert["INHG"]["PSF"] = 70.7180803;
    convert["PSF"]["INHG"] = 1.0/convert["INHG"]["PSF"];
    convert["ATM"]["INHG"] = 29.9246899;
    convert["INHG"]["ATM"] = 1.0/convert["ATM"]["INHG"];
    convert["PSI"]["INHG"] = 2.03625437;
    convert["INHG"]["PSI"] = 1.0/convert["PSI"]["INHG"];
    convert["INHG"]["PA"] = 3386.0; // inches Mercury to pascals
    convert["PA"]["INHG"] = 1.0/convert["INHG"]["PA"];
    convert["LBS/FT2"]["N/M2"] = 14.5939/convert["FT"]["M"];
    convert["N/M2"]["LBS/FT2"] = 1.0/convert["LBS/FT2"]["N/M2"];
    convert["LBS/FT2"]["PA"] = convert["LBS/FT2"]["N/M2"];
    convert["PA"]["LBS/FT2"] = 1.0/convert["LBS/FT2"]["PA"];
    // Mass flow
    convert["KG/MIN"]["LBS/MIN"] = convert["KG"]["LBS"];
    // Fuel Consumption
    convert["LBS/HP*HR"]["KG/KW*HR"] = 0.6083;
    convert["KG/KW*HR"]["LBS/HP*HR"] = 1.0/convert["LBS/HP*HR"]["KG/KW*HR"];
    // Density
    convert["KG/L"]["LBS/GAL"] = 8.3454045;
    convert["LBS/GAL"]["KG/L"] = 1.0/convert["KG/L"]["LBS/GAL"];

    // Length
    convert["M"]["M"] = 1.00;
    convert["KM"]["KM"] = 1.00;
    convert["FT"]["FT"] = 1.00;
    convert["IN"]["IN"] = 1.00;
    // Area
    convert["M2"]["M2"] = 1.00;
    convert["FT2"]["FT2"] = 1.00;
    // Volume
    convert["IN3"]["IN3"] = 1.00;
    convert["CC"]["CC"] = 1.0;
    convert["M3"]["M3"] = 1.0;
    convert["FT3"]["FT3"] = 1.0;
    convert["LTR"]["LTR"] = 1.0;
    // Mass & Weight
    convert["KG"]["KG"] = 1.00;
    convert["LBS"]["LBS"] = 1.00;
    // Moments of Inertia
    convert["KG*M2"]["KG*M2"] = 1.00;
    convert["SLUG*FT2"]["SLUG*FT2"] = 1.00;
    // Angles
    convert["DEG"]["DEG"] = 1.00;
    convert["RAD"]["RAD"] = 1.00;
    // Angular rates
    convert["DEG/SEC"]["DEG/SEC"] = 1.00;
    convert["RAD/SEC"]["RAD/SEC"] = 1.00;
    // Spring force
    convert["LBS/FT"]["LBS/FT"] = 1.00;
    convert["N/M"]["N/M"] = 1.00;
    // Damping force
    convert["LBS/FT/SEC"]["LBS/FT/SEC"] = 1.00;
    convert["N/M/SEC"]["N/M/SEC"] = 1.00;
    // Damping force (Square law)
    convert["LBS/FT2/SEC2"]["LBS/FT2/SEC2"] = 1.00;
    convert["N/M2/SEC2"]["N/M2/SEC2"] = 1.00;
    // Power
    convert["HP"]["HP"] = 1.00;
    convert["WATTS"]["WATTS"] = 1.00;
    // Force
    convert["N"]["N"] = 1.00;
    // Velocity
    convert["FT/SEC"]["FT/SEC"] = 1.00;
    convert["KTS"]["KTS"] = 1.00;
    convert["M/S"]["M/S"] = 1.0;
    convert["M/SEC"]["M/SEC"] = 1.0;
    convert["KM/SEC"]["KM/SEC"] = 1.0;
    // Torque
    convert["FT*LBS"]["FT*LBS"] = 1.00;
    convert["N*M"]["N*M"] = 1.00;
    // Valve
    convert["M4*SEC/KG"]["M4*SEC/KG"] = 1.0;
    convert["FT4*SEC/SLUG"]["FT4*SEC/SLUG"] = 1.0;
    // Pressure
    convert["PSI"]["PSI"] = 1.00;
    convert["PSF"]["PSF"] = 1.00;
    convert["INHG"]["INHG"] = 1.00;
    convert["ATM"]["ATM"] = 1.0;
    convert["PA"]["PA"] = 1.0;
    convert["N/M2"]["N/M2"] = 1.00;
    convert["LBS/FT2"]["LBS/FT2"] = 1.00;
    // Mass flow
    convert["LBS/SEC"]["LBS/SEC"] = 1.00;
    convert["KG/MIN"]["KG/MIN"] = 1.0;
    convert["LBS/MIN"]["LBS/MIN"] = 1.0;
    // Fuel Consumption
    convert["LBS/HP*HR"]["LBS/HP*HR"] = 1.0;
    convert["KG/KW*HR"]["KG/KW*HR"] = 1.0;
    // Density
    convert["KG/L"]["KG/L"] = 1.0;
    convert["LBS/GAL"]["LBS/GAL"] = 1.0;
  }
  attribute_key.resize(0);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Element::~Element(void)
{
  for (unsigned int i=0; i<children.size(); i++) delete children[i];
  data_lines.clear();
  attributes.clear();
  attribute_key.clear();
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

string Element::GetAttributeValue(const string& attr)
{
  if (HasAttribute(attr))  return attributes[attr];
  else                     return ("");
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

bool Element::HasAttribute(const string& attr)
{
  bool status=true;
  int select=-1;

  unsigned int attr_cnt = attribute_key.size();

  for (unsigned int i=0; i<attr_cnt; i++) {
    if (attribute_key[i] == attr) select = i;
  }
  if (select < 0) status=false;
  return status;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::GetAttributeValueAsNumber(const string& attr)
{
  string attribute = GetAttributeValue(attr);

  if (attribute.empty()) return HUGE_VAL;
  else {
    double number=0;
    if (is_number(trim(attribute)))
      number = atof(attribute.c_str());
    else
      throw("Expecting numeric attribute value, but got: " + attribute);
    
    return (number);
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Element* Element::GetElement(unsigned int el)
{
  if (children.size() > el) {
    element_index = el;
    return children[el];
  }
  else {
    element_index = 0;
    return 0L;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Element* Element::GetNextElement(void)
{
  if (children.size() > element_index+1) {
    element_index++;
    return children[element_index];
  } else {
    element_index = 0;
    return 0L;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

string Element::GetDataLine(unsigned int i)
{
  if (data_lines.size() > 0) return data_lines[i];
  else return string("");
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::GetDataAsNumber(void)
{
  if (data_lines.size() == 1) {
    double number=0;
    if (is_number(trim(data_lines[0])))
      number = atof(data_lines[0].c_str());
    else
      throw("Expected numeric value, but got: " + data_lines[0]);

    return number;
  } else if (data_lines.size() == 0) {
    return HUGE_VAL;
  } else {
    cerr << "Attempting to get single data value from multiple lines in element " << name << endl;
    return HUGE_VAL;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

unsigned int Element::GetNumElements(const string& element_name)
{
  unsigned int number_of_elements=0;
  Element* el=FindElement(element_name);
  while (el) {
    number_of_elements++;
    el=FindNextElement(element_name);
  }
  return number_of_elements;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Element* Element::FindElement(const string& el)
{
  if (el.empty() && children.size() >= 1) {
    element_index = 1;
    return children[0];
  }
  for (unsigned int i=0; i<children.size(); i++) {
    if (el == children[i]->GetName()) {
      element_index = i+1;
      return children[i];
    }
  }
  element_index = 0;
  return 0L;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Element* Element::FindNextElement(const string& el)
{
  if (el.empty()) {
    if (element_index < children.size()) {
      return children[element_index++];
    } else {
      element_index = 0;
      return 0L;
    }
  }
  for (unsigned int i=element_index; i<children.size(); i++) {
    if (el == children[i]->GetName()) {
      element_index = i+1;
      return children[i];
    }
  }
  element_index = 0;
  return 0L;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::FindElementValueAsNumber(const string& el)
{
  Element* element = FindElement(el);
  if (element) {
    double value = element->GetDataAsNumber();
    value = DisperseValue(element, value);
    return value;
  } else {
    cerr << "Attempting to get single data value from multiple lines" << endl;
    return 0;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

string Element::FindElementValue(const string& el)
{
  Element* element = FindElement(el);
  if (element) {
    return element->GetDataLine();
  } else {
    return "";
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::FindElementValueAsNumberConvertTo(const string& el, const string& target_units)
{
  Element* element = FindElement(el);

  if (!element) {
    cerr << "Attempting to get non-existent element " << el << endl;
    exit(0);
  }

  string supplied_units = element->GetAttributeValue("unit");

  if (!supplied_units.empty()) {
    if (convert.find(supplied_units) == convert.end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" does not exist (typo?). Add new unit"
           << " conversion in FGXMLElement.cpp." << endl;
      exit(-1);
    }
    if (convert[supplied_units].find(target_units) == convert[supplied_units].end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" cannot be converted to "
                   << target_units << ". Add new unit conversion in FGXMLElement.cpp or fix typo" << endl;
      exit(-1);
    }
  }

  double value = element->GetDataAsNumber();
  if (!supplied_units.empty()) {
    value *= convert[supplied_units][target_units];
  }

  value = DisperseValue(element, value, supplied_units, target_units);

  return value;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::FindElementValueAsNumberConvertFromTo( const string& el,
                                                       const string& supplied_units,
                                                       const string& target_units)
{
  Element* element = FindElement(el);

  if (!element) {
    cerr << "Attempting to get non-existent element " << el << endl;
    exit(0);
  }

  if (!supplied_units.empty()) {
    if (convert.find(supplied_units) == convert.end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" does not exist (typo?). Add new unit"
           << " conversion in FGXMLElement.cpp." << endl;
      exit(-1);
    }
    if (convert[supplied_units].find(target_units) == convert[supplied_units].end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" cannot be converted to "
                   << target_units << ". Add new unit conversion in FGXMLElement.cpp or fix typo" << endl;
      exit(-1);
    }
  }

  double value = element->GetDataAsNumber();
  if (!supplied_units.empty()) {
    value *= convert[supplied_units][target_units];
  }

  value = DisperseValue(element, value, supplied_units, target_units);

  return value;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

FGColumnVector3 Element::FindElementTripletConvertTo( const string& target_units)
{
  FGColumnVector3 triplet;
  Element* item;
  double value=0.0;
  string supplied_units = GetAttributeValue("unit");

  if (!supplied_units.empty()) {
    if (convert.find(supplied_units) == convert.end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" does not exist (typo?). Add new unit"
           << " conversion in FGXMLElement.cpp." << endl;
      exit(-1);
    }
    if (convert[supplied_units].find(target_units) == convert[supplied_units].end()) {
      cerr << endl << "Supplied unit: \"" << supplied_units << "\" cannot be converted to "
                   << target_units << ". Add new unit conversion in FGXMLElement.cpp or fix typo" << endl;
      exit(-1);
    }
  }

  item = FindElement("x");
  if (!item) item = FindElement("roll");
  if (item) {
    value = item->GetDataAsNumber();
    if (!supplied_units.empty()) value *= convert[supplied_units][target_units];
    triplet(1) = DisperseValue(item, value, supplied_units, target_units);
  } else {
    triplet(1) = 0.0;
  }
  

  item = FindElement("y");
  if (!item) item = FindElement("pitch");
  if (item) {
    value = item->GetDataAsNumber();
    if (!supplied_units.empty()) value *= convert[supplied_units][target_units];
    triplet(2) = DisperseValue(item, value, supplied_units, target_units);
  } else {
    triplet(2) = 0.0;
  }

  item = FindElement("z");
  if (!item) item = FindElement("yaw");
  if (item) {
    value = item->GetDataAsNumber();
    if (!supplied_units.empty()) value *= convert[supplied_units][target_units];
    triplet(3) = DisperseValue(item, value, supplied_units, target_units);
  } else {
    triplet(3) = 0.0;
  }

  return triplet;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::DisperseValue(Element *e, double val, const std::string supplied_units, const std::string target_units)
{
  double value=val;
  double disp=0.0;
  if (e->HasAttribute("dispersion")) {
    disp = e->GetAttributeValueAsNumber("dispersion");
    if (!supplied_units.empty()) disp *= convert[supplied_units][target_units];
    string attType = e->GetAttributeValue("type");
    if (attType == "gaussian") {
      value = val + disp*GaussianRandomNumber();
    } else if (attType == "uniform") {
      value = val + disp * ((((double)rand()/RAND_MAX)-0.5)*2.0);
    } else {
      std::cerr << "Unknown dispersion type" << endl;
      throw("Unknown dispersion type");
    }

  }
  return value;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

double Element::GaussianRandomNumber(void)
{
  static double V1, V2, S;
  static int phase = 0;
  double X;

  if (phase == 0) {
    V1 = V2 = S = X = 0.0;

    do {
      double U1 = (double)rand() / RAND_MAX;
      double U2 = (double)rand() / RAND_MAX;

      V1 = 2 * U1 - 1;
      V2 = 2 * U2 - 1;
      S = V1 * V1 + V2 * V2;
    } while(S >= 1 || S == 0);

    X = V1 * sqrt(-2 * log(S) / S);
  } else
    X = V2 * sqrt(-2 * log(S) / S);

  phase = 1 - phase;

  return X;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void Element::Print(unsigned int level)
{
  unsigned int i, spaces;

  level+=2;
  for (spaces=0; spaces<=level; spaces++) cout << " "; // format output
  cout << "Element Name: " << name;
  for (i=0; i<attributes.size(); i++) {
    cout << "  " << attribute_key[i] << " = " << attributes[attribute_key[i]];
  }
  cout << endl;
  for (i=0; i<data_lines.size(); i++) {
    for (spaces=0; spaces<=level; spaces++) cout << " "; // format output
    cout << data_lines[i] << endl;
  }
  for (i=0; i<children.size(); i++) {
    children[i]->Print(level);
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void Element::AddAttribute(const string& name, const string& value)
{
  attribute_key.push_back(name);
  attributes[name] = value;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void Element::AddData(string d)
{
  string::size_type string_start = d.find_first_not_of(" \t");
  if (string_start != string::npos && string_start > 0) {
    d.erase(0,string_start);
  }
  data_lines.push_back(d);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

} // end namespace JSBSim