/// <summary>
/// Unify given expressions using tokens
/// </summary>
/// <param name="input1">first expression</param>
/// <param name="input2">second expression</param>
/// <param name="tokens">array of tokens to match</param>
/// <returns>most general unifier</returns>
public static IExpression Unify(string input1, string input2, params Token[] tokens)
{
var l1 = new Lexer(input1, tokens);
var l2 = new Lexer(input2, tokens);
return Unify(Eval(ref l1), Eval(ref l2));
}
/// <summary>
/// Consumes Tokens from Lexer l until a expression is paresed completely
/// </summary>
/// <param name="l">Lexical analyzer if the expression to parse</param>
/// <returns>parsed expression</returns>
public static IExpression Eval(ref Lexer l)
{
if (!l.Next()) return null;
IExpression expr;
do
{
EvalToken(ref l, out expr);
} while (expr == null && l.Next());
return expr;
}
/// <summary>
/// Consume next token
/// </summary>
/// <param name="l">the lexer</param>
/// <param name="expr">output expression</param>
static void EvalToken(ref Lexer l, out IExpression expr)
{
switch (l.Token)
{
case Token.QuotedString:
case Token.Float:
case Token.Int:
case Token.False:
case Token.True:
if (FuncStack.Count == 0)
{
expr = new ValueExpression(l.Value);
return;
}
ParamStack.Peek().Add(new ValueExpression(l.Value));
break;
case Token.Variable:
if (FuncStack.Count == 0)
{
expr = new VariableExpression(l.Value);
return;
}
ParamStack.Peek().Add(new VariableExpression(l.Value));
break;
case Token.Function:
FuncStack.Push(l.Value);
break;
case Token.LeftBrace:
ParamStack.Push(new List<IExpression>());
break;
case Token.RightBrace:
if(FuncStack.Count == 1)
{
var p = ParamStack.Pop().ToArray();
expr = new FunctionExpression(FuncStack.Pop(), p);
return;
}
var param = ParamStack.Pop().ToArray();
ParamStack.Peek().Add(new FunctionExpression(FuncStack.Pop(),param));
break;
case Token.Comma:
case Token.Dot:
case Token.Space:
break;
default:
throw new ArgumentOutOfRangeException();
}
expr = null;
}