private IExpression Parse(TokenOrExpression tokenOrExpression)
{
if (tokenOrExpression.Expression != null)
{
return(tokenOrExpression.Expression);
}
return(Parse(tokenOrExpression.Token));
}
private bool TryParseVariableReference(List <TokenOrExpression> tokens)
{
if (Matches(tokens, TokenType.Dollar, TokenType.Literal))
{
TokenOrExpression name = tokens[1];
tokens.RemoveRange(0, 2);
tokens.Insert(0, new TokenOrExpression(CreateVariableExpression(name.Token.Value)));
return(true);
}
return(false);
}
private IExpression Parse(IEnumerable <Token> tokens)
{
var stack = new List <TokenOrExpression>();
int highestPrecedence = 0;
using (IEnumerator <Token> iterator = tokens.GetEnumerator())
{
while (iterator.MoveNext())
{
Token token = iterator.Current;
if (token.Type == TokenType.Whitespace)
{
continue;
}
if (IsOperator(token.Type))
{
int precedence = Precedence(token.Type);
if (precedence < highestPrecedence)
{
TryParseLeftToRight(stack);
}
stack.Add(token);
highestPrecedence = precedence;
}
else if (token.Type == TokenType.Quotation)
{
var stringTokens = FindTokensInString(iterator);
stack.Add(new TokenOrExpression(StringLiteral.Create(stringTokens)));
}
else
{
stack.Add(token);
}
}
}
if (stack.Count == 0)
{
return(null);
}
if (!TryParseLeftToRight(stack))
{
throw new ParseException();
}
TokenOrExpression tok = stack[0];
return(tok.Expression);
}
private bool TryParseLiteral(List <TokenOrExpression> tokens)
{
if (Matches(tokens, TokenType.True))
{
tokens[0] = new TokenOrExpression(new BoolLiteral(true));
return(true);
}
if (Matches(tokens, TokenType.False))
{
tokens[0] = new TokenOrExpression(new BoolLiteral(false));
return(true);
}
if (Matches(tokens, TokenType.Literal))
{
tokens[0] = new TokenOrExpression(Literal.Create(tokens[0].Token.Value));
return(true);
}
return(false);
}
private bool TryParseOne(List <TokenOrExpression> tokens)
{
if (TryParseVariableReference(tokens))
{
return(true);
}
if (TryParseBinaryOperation(tokens))
{
return(true);
}
if (TryParseUnaryOperation(tokens))
{
return(true);
}
if (TryParseLiteral(tokens))
{
return(true);
}
if (tokens.Count >= 1)
{
if (tokens[0].Expression != null)
{
return(true);
}
if (tokens[0].Token.Type == TokenType.Literal)
{
tokens[0] = new TokenOrExpression(new StringLiteral(tokens[0].Token.Value));
return(true);
}
}
return(false);
}
private bool TryParseBinaryOperation(List <TokenOrExpression> tokens)
{
if (tokens.Count >= 3 && IsBinaryOperator(tokens[1].Token.Type, out var operation))
{
// Binary expression
TokenOrExpression lhs = tokens[0];
tokens.RemoveRange(0, 2);
TryParseLeftToRight(tokens);
if (tokens.Count != 1)
{
throw new ParseException();
}
IExpression leftHandSide = Parse(lhs);
IExpression rightHandSide = tokens[0].Expression;
var expression = BinaryExpression.Create(operation, leftHandSide, rightHandSide);
tokens.RemoveAt(0);
tokens.Insert(0, new TokenOrExpression(expression));
return(true);
}
return(false);
}
