public Parser(Tokenizer tokenizer)
{
Debug.Assert(tokenizer != null);
this.tokenizer = tokenizer;
this.ReadNextToken();
}
// turn the expression into an AST each time it changes (not each time our Convert methods are called)
private void EnsureExpressionNode()
{
if (this.expressionNode != null || string.IsNullOrEmpty(this.expression))
{
return;
}
using (var stringReader = new StringReader(this.expression))
using (var tokenizer = new Tokenizer(stringReader))
using (var parser = new Parser(tokenizer))
{
this.expressionNode = parser.ParseExpression();
}
}