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;
}
private ArithOp ParseOperator( Tokens tokens )
{
if ( tokens.PullTokenIfEqual ( "+" ) )
{
return ArithOp.Add;
}
else if ( tokens.PullTokenIfEqual ( "-" ) )
{
return ArithOp.Sub;
}
else if ( tokens.PullTokenIfEqual ( "*" ) )
{
return ArithOp.Mul;
}
else if ( tokens.PullTokenIfEqual ( "/" ) )
{
return ArithOp.Div;
}
else if ( tokens.PullTokenIfEqual ( "==" ) )
{
return ArithOp.Equality;
}
else if ( tokens.PullTokenIfEqual ( "<" ) )
{
return ArithOp.LessThan;
}
else if ( tokens.PullTokenIfEqual ( ">" ) )
{
return ArithOp.GreaterThan;
}
return ArithOp.none;
}
