anchor.diff:  export 'mathutil.functions.dart';
   export 'mathutil.constants.dart';
   
  +
   /// This RegExp matches all numbers including scientific notations.
   RegExp regexNumber   = new RegExp(r"(?:\d*\.)?\d+(?:e(?:\+|-)?\d+)?");
   /// This RegExp matches all expressions that contain no equality operator (´=´).
  
positive.code: /// This RegExp matches mathematic representations of funktions (e.g. ´f(x)=x^2´).
  RegExp regexFunction = new RegExp(r"([a-z]+)\(([A-Za-z]+)\)\s*=\s*(.+)$");
  
  List controlchars = ['(', ',', ')', ';'];
  
  /// These function convert numbers between different angle units.
  double degtorad(a) {
  
negative.code: double gradtorad(a) {
    return (a / 200) * math.PI;
  }
  
  
  /// This function checks a given String against the [regexNumber] RegExp.
  bool isNumber(String exp) {
    return regexNumber.hasMatch(exp);
  }
  /// This function checks a given String against the [regexTerm] RegExp.
  bool isTerm(String exp) {
    return regexTerm.hasMatch(exp);
  }
  /// This function checks a given String against the [regexFunction] RegExp.
  bool isFunction(String exp) {
    return regexFunction.hasMatch(exp);
  }
  