/// <summary>
/// Split an expression into tokens
/// </summary>
public static List<Token> Tokens(this string input)
{
// (strings) | (nums, funcs, vars) | (sci nums)
var r = new Regex(@"(\['.*?'\])|([^0-9a-zA-Z.\$])|([0-9.]+e[+\-]?[0-9]+)");
// anything but alpha numeric or decimals gets split
var output = new List<Token>();
// return splits, including split characters (because of capture group in regex)
string[] frags = r.Split(input);
foreach (string frag in frags) {
if (String.IsNullOrEmpty(frag)) continue;
var t = new Token(frag);
var last = (output.Count > 0) ? (output.Last()) : (null);
#region check for uniary prefix operators
if (t.Class == TokenClass.BinaryOperator) {
if (output.Count < 1) {
t.Class = TokenClass.UniaryPrefix;
} else {
if (last != null)
switch (last.Class) {
case TokenClass.BinaryOperator:
case TokenClass.UniaryPostfix:
case TokenClass.OpenBracket:
case TokenClass.ArgumentSeperator:
t.Class = TokenClass.UniaryPrefix;
break;
}
}
}
#endregion
#region check for functions
// a name followed by an open bracket is taken to be a function
if (last != null)
if (t.Class == TokenClass.OpenBracket
&& output.Count > 0
&& last.Class == TokenClass.Name) {
last.Class = TokenClass.Function;
last.Value = "/" + last; // easier to find functions, plus vars and fucntions can share a name
}
#endregion
output.Add(t);
}
return output;
}
/// <summary>
/// Compare precedence, taking associativity into account
/// </summary>
public bool ShouldDisplace(Token other)
{
if (other.Class != TokenClass.BinaryOperator) return false;
if (Direction == Association.LeftToRight) {
return other.Precedence >= Precedence;
}
return other.Precedence > Precedence;
}