Are contributions accepted? Have a few ideas.

[srd4]

I saw your comment on r/python today. Coincidentally I worked last week in something similar after being introduced to propositional logic at a discrete maths course. I'm interested in collaborating and thought about some ideas and improvements:

• Implementing truth tables. This can be used to verify equivalence between different formulas.
• Using english words as conectives to join formulas, i.e, ~a && b being posible to write as not a and b (and complexer) and to be recognized. This wouldn't be difficult given how well your implementation seems to be written, kudos for that.
• Documenting the code and make it a bit more readable for people who want to collaborate.

Totally up for helping with the project if you want help at all. Thanks for reading, and have a good day!!

[lion137]

Hi, Thanks for interest and feedback.

• Equivalence, this could be simply done : (F1) <=> (F2), means F1 and F2 are equivalent.
• Changing operators to English words, seems to only some refactoring of scanner, but it's tricky in later phases algorithm make usage of that, that some tokens are letters - so after scanning and tokenizing, and, or, not should be changed back to symbols (less work with refactoring parser and evaluate) back ;however it looks OK for ~ -> not, && -> and, || -> or, but I'm not sure, that sure, that it improves readability for: =>, <=>, change to: ifthen, equivalent? Or could be left as it is, with changing only the mentioned.
• Documentation, yes, it's good idea, I'm now hunting a bug, which I've introduced while adding formula checking functions:) If I find time, I'll try to fix it this week. If be done, next thing is documentation. If you want to help, first, I will make some basic comments to make easier navigate trough the code and you can try to work on changed version (to English words). Here is great explanation of the algorithms used (I was using it): https://runestone.academy/runestone/books/published/pythonds/BasicDS/InfixPrefixandPostfixExpressions.html on craftinginterpreters.com you find information about scanning. One more thanks, let me know what you think. Have a good evening!

On Sat, 2 Nov 2019 at 21:42, Daniel Gil notifications@github.com wrote:

I saw your comment on r/python today. Coincidentally I worked last week in something similar after being introduced to propositional logic at a discrete maths course. I'm interested in collaborating and thought about some ideas and improvements:

• Implementing truth tables. This can be used to verify equivalence between different formulas.
• Using english words as conectives to join formulas, i.e, ~a && b being posible to write as "not a and b" (and complexer) and to be recognized. This wouldn't be difficult given how well your implementation seems to be written, kudos for that.
• Documenting the code and make it a bit more readable for people who want to collaborate.

Totally up for helping with the project if you want help at all. Thanks for reading, and have a good day!!

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[srd4]

I actually couldn't help and play with the code a bit yasterday. As I said, I'm taking a course on discrete maths and wanted to try a few expressions I had on my notes. I noticed that it was a bit slow to write symbols (or I'm just not used to it, I guess) I do type quite fast and wanted to try many expressions so I beggan analysing the code and found an easy way arround it. Didn't event need to touch the rest of the stuff:

def replaceEnglish(formula):
    #Replaces english operators in formula with equivalent symbols.
    equivalences = dict({"not":"~", "and":"&&", "or":"||", "if only if":"<=>","only if":"<=>", "then":"=>"})

    for equivalence in equivalences:
        if equivalence in formula:
            formula = formula.replace(equivalence,equivalences[equivalence])

    return formula

User input just needs to be passed here once and there'll be no problem with the rest of the code.

• What I meant by equivalence was a bit broader than that. In the course they teached us to do this kind of "algebra" with formulas to prove equivalences using de morgan laws and so on. When you do this, just like in algebra, you transform an expression into different versions of it until you find the second formula of the equivalence stated at the beggining. I wanted the program to be able to take several of these equations and tell me about any errors in the whole procedure. Also achieved this, with a rather not so elegant couple functions tho.

I don't want to paste the whole thing here so take, for example, that to prove the equivalence (~ p => ~ q) <=> (q => p) I would make something like "not p then not q == p or not q == not q or p == q then p" and want to know if I made any mistakes along the way:

> not p then not q == p or not q == not q or p  == q then p
Formulas are equal
> not p then not q == p or not q == not q or p  == q then x
q then x is not equal

As I say, I managed to make it work, and also is using messages from your check() to reference a specific error on formulas:

> a or not a == weird a
Invalid symbols on formula 2

Other than that, I noticed a few minimal redundancies on the code and have due to understand how eval and parse really work, also made a different version of the tokenize function and moved some stuff repl function to make it all work, mainly because of the changes I was making but also noticed that the help commands where not working and corrected it too. The comments you say would really help. You made a good job making the mechanics of this thing. And I'm telling you because I tried it myself a few days ago lol.

I'm willing to collaborate as much as I can, actually learned a bunch of stuff just messing with it and want to keep learning even more! I guess I'll be reading what you sent, tell me if you want to see more of what I implemented.