public void TestSetRollbackPoint()
{
Tokens tokens = new Tokens();
tokens.AddTokens ( new string[] { "1", "2", "3", "4", "5" } );
Assert.AreEqual ( "1", tokens.PeekToken () );
tokens.SetMark ();
Assert.AreEqual ( "1", tokens.PullToken () );
Assert.AreEqual ( "2", tokens.PullToken () );
Assert.AreEqual ( "3", tokens.PullToken () );
tokens.RollbackToMark ();
Assert.AreEqual ( "1", tokens.PeekToken () );
}
public bool TryParse(Tokens tokens, IScope scope, out IStatement statement)
{
tokens.SetMark ();
Expression value = _expressionParser.ParseValue ( scope, tokens );
// Look ahead to see if this is an assignment
if ( value is Variable && tokens.PullTokenIfEqual ( "=" ) )
{
Assign assign = new Assign ( _executorFactory.GetAssignExecutor() );
assign.Ident = value as Variable;
Expression expression = _expressionParser.ParseExpression ( scope, tokens );
assign.Expr = expression;
statement = assign;
return true;
}
// Failed to parse as assignment, rollback.
tokens.RollbackToMark ();
statement = null;
return false;
}