Truth table using recursion

Question

i am trying to create a truth table in c# for 3 symbols so it should produce 2^3 = 8 tables. but my recursive method is not working.

My code is below. in each loop i add a symbol and make new dictionary with one true and one false value.

    public void TTEntails()
    {
        Queue<string> s = new Queue<string>();
        s.Enqueue("p");
        s.Enqueue("q");
        s.Enqueue("r");
        TTCheckAll(s, new Dictionary<string, bool>());
    }


    public void TTCheckAll(Queue<string> symbol, Dictionary<string, bool> model)
    {
        if (symbol.Count == 0)
        {
            PLTrue(model);
        }
        else
        {
            string topSymbol = symbol.Dequeue();
            TTCheckAll(symbol, ReturnDict(model, topSymbol, true));
            TTCheckAll(symbol, ReturnDict(model, topSymbol, false));
        }
    }

    private Dictionary<string, bool> ReturnDict(Dictionary<string, bool> model, string key, bool value)
    {
        Dictionary<string, bool> newDict = new Dictionary<string, bool>(model);
        newDict.Add(key, value);
        return newDict;
    }

the result produced is as follows:

p, True
q, True
r, True


p, True
q, True
r, False


p, True
q, False


p, False

the result should be

p, True
q, True
r, True

p, True
q, True
r, false

p, True
q, false
r, True

p, True
q, false
r, false

p, false
q, True
r, True

p, false
q, True
r, false

p, false
q, false
r, True

p, false
q, false
r, false

And for those of us playing-at-home, what should the results look like — TheGeneral, May 24 '19 at 06:19
i am just printing the truth table in it for now. once i get the complete truth table ill proceed. thanks — Aseem Malhotra, May 24 '19 at 06:32
Well, the results are exactly what I'd expect from that code. Have you tried step-by-step debugging? Either that recursion is not even close to what you are looking for or you got some data type wrong — Camilo Terevinto, May 24 '19 at 06:34
i did changed the data type. instead of method TTCheckAll() was a bool and return was (TTCheckAll(true) && TTCheckAll(false)). but the result was the same. — Aseem Malhotra, May 24 '19 at 06:40

score 2 · Accepted Answer · answered May 24 '19 at 08:08

You need to pass a copy of a queue to each true/false branch:

public void TTCheckAll(Queue<string> symbol, Dictionary<string, bool> model)
{
    if (symbol.Count == 0)
    {
        PLTrue(model);
    }
    else
    {
        string topSymbol = symbol.Dequeue();
        TTCheckAll(new Queue<string>(symbol), ReturnDict(model, topSymbol, true));
        TTCheckAll(new Queue<string>(symbol), ReturnDict(model, topSymbol, false));
    }
}

score 0 · Answer 2 · answered May 24 '19 at 07:15

0

Change with this.

 public void TTCheckAll(Queue<string> symbol, Dictionary<string, bool> model,bool value )
{
    if (symbol.Count == 0)
    {
        PLTrue(model);
    }
    else
    {
        string topSymbol = symbol.Dequeue();
        TTCheckAll(symbol, ReturnDict(model, topSymbol, value),(value?false:true));

    }
}

answered May 24 '19 at 07:15

Mehmet Ordu

53
5

i tried it but it just produces 1 truth table not 8 – Aseem Malhotra May 24 '19 at 08:02

Truth table using recursion

2 Answers2