Talk:Interpreter pattern

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What does the link "Block (Java programming language)" mean? It points to nowhere. Lathspell 18:12, 18 February 2006 (UTC)[reply]

I doubt that the interpreter patter is described correctly since this page describes it very differently. http://www.exciton.cs.rice.edu/JAvaResources/DesignPatterns/intepreter.htm 80.141.90.99 13:35, 8 June 2007 (UTC) see also http://home.earthlink.net/~huston2/dp/interpreter.html 80.141.90.99 13:37, 8 June 2007 (UTC)[reply]

I dont know what you mean, the operation() method is replaced by the execute() method, the concept is exactly the same.

--98.225.38.255 (talk) 23:25, 13 February 2010 (UTC) I think the C# (and probably Java version is wrong). The problem is in Evaluator function, the left and right operands are switched. If you compute 6 - 4 or 6 4 - , the result that you get is 4 - 6. The solution is [reply]

                       IExpression r = stack.Pop();
                       IExpression l = stack.Pop();
                       stack.Push(new Plus(l, r));

instead of

                       stack.Push(new Plus(stack.Pop(), stack.Pop()));

Corrected code:

           public Evaluator(string expression)
           {
               Stack<IExpression> stack = new Stack<IExpression>();
               foreach (string token in expression.Split(' '))
               {
                   if (token.Equals("+"))
                   {
                       IExpression r = stack.Pop();
                       IExpression l = stack.Pop();
                       stack.Push(new Plus(l, r));
                   }
                   else if (token.Equals("-"))
                   {
                       IExpression r = stack.Pop();
                       IExpression l = stack.Pop();
                       stack.Push(new Minus(l, r));
                   }
                   else
                       stack.Push(new Variable(token));
               }
               syntaxTree = stack.Pop();
           }

Go language

If we ever wanted to supply an example of this pattern in the Go language , this may be a good starting point. Bovlb (talk) 20:06, 15 January 2010 (UTC)[reply]

Errors in diagram

The "Interpret(Context)" methods in TerminalExpression and NonTerminalExpression are in italics, which indicates they are abstract. Clearly they are meant to be concrete implementations of the abstract method "Interpret(Context)" in AbstractExpression. The "Interpret(Context)" should have italics removed in the *subclasses*. 14:41, 15 April 2012 (UTC) — Preceding unsigned comment added by 78.105.136.120 (talk) It has come to my attention that if this is a GoF diagram then it is probably in OMT and not UML. My reasoning above is for the UML diagram, I am not aware of correctness for OMT. I'll leave the comment above just in case some other unassuming developer comes across here and expects to be seeing UML. :)