Truth table program

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Summary:

Interpret a string and generate and display a truth table.

Truth table program

ConorOBrien 04 Jul 2015 00:25

I've coded a program (TI-BASIC, not assembly) that will take the user's input for a Boolean expression, and I need to interpret this expression to make a truth table. The user can use any of the 27 keyboard values (A-Z + θ).

I want to display a truth table of this general form:

(1)

\begin{array} {c|c|c}p&q&\phi(p,q)\\\hline 1&1&?\\1&0&?\\0&1&?\\0&0&? \end{array}

Where $\phi(p,q)$ is the user's input. I know I need to limit the variables (as, if the user used ALL 27 VARIABLES, I would need $2^{27}=134217728$ rows, a ridiculous amount), but how might I generate the truth table?

The user's input may look something like this:

"P or Q and not(R) xor not(P)"            ;this is stored in Str1

The only rows I would need to display are $p,\ldots,\theta$ (or maybe less variables) and $\phi(\vec{v_i})$ (the user's input). I would appreciate any help on this. Thanks!

Re: Truth table program

Trenly 04 Jul 2015 05:37

A few questions…

1) How are you going to display a large table? Are you going to use the graph screen?
2) will it have decent size, speed, and reliability
3) why? Truth tables are fairly straightforward and easy

Re: Truth table program

ConorOBrien 05 Jul 2015 20:29

1) Yes, I am going to use the graph screen.
2) It should.
3) They are indeed. It is mainly my exploration into app-making; practice makes perfect!

Re: Truth table program

kgmstwo 14 Jul 2015 10:03

Just generating the results here is kinda tricky.

What we want is to run expr( on Str1 after we have stored the values we want to evaluate into the variables that are used. Seems simple enough- you can do this with a For(P,0,1 for each variable that is used.
But here's the hard part, how can we tell what variables are used? Sure, there are many ways to get the name variables used stored into a string, but now what? As far as I know, there's no way to indirectly store to a variable, so we're out of luck. The best solution I've got is assign every variable in Str1 a number, then go through Str1 and replace each occurance with L₁(number). Now you can loop through L₁, and expr(Str1 will work.

I'd suggest don't bother with the graph screen, since it won't actually get you any more variables than the homescreen. Instead, try allowing the user to scroll up and down, and generate only the variables needed for display. I think this is a cool program idea.