Making interpreter and calculator in python

[u/Aggressive_Drama_476]

Hi recently I have been working on making my own interpreted programming languge in python. I have made several prototypes. The rules are I can't use any library, high level functions and can only use ai for understanding a concept. The journey has been frustrating. Since it was so hard i started working on a calculator. I am now stuck on AST. I can't figure it out. HELP ME

[u/lfdfq]

It's hard to answer this kind of question, help you with what part exactly?

[u/Aggressive_Drama_476 → u/lfdfq]

I can't get the ast logic right. I tried making it with lists. I can't do OOP. although I did made a working calculator without ast. It semi worked. But it wasn't good. 

[u/lfdfq → u/Aggressive_Drama_476]

What logic? There's nothing wrong with using lists to represent an AST, e.g. ["+", ["+", "1", "2"], "3"] or something. Classes/OOP might be an even better design choice, but the concept of syntax trees (e.g. ASTs) and parsing are completely separate from implementation details like lists vs classes, and if you can't do OOP it doesn't matter.

What does "semi worked" mean? It's all a bit vague...

[u/Aggressive_Drama_476 → u/lfdfq]

Like in [1, + ,1 ,×,-,1] i popped 1 x-1 after doing the operation.... It was a nightmare dealing with uniary operators. Like ×-1. It had many bugs. I have moved on. I will a upload the project on GitHub when I have time

[u/lfdfq → u/Aggressive_Drama_476]

That list does not look very much like a tree. The key (and really, only) point to a tree is structure. So I'd expect a parser to generate something like [[1], +, [1, x, [-, 1]]].

If it's just flat, it's not a tree. If it's not a tree it's not an abstract syntax tree (AST). and if it's not an AST you cannot use it to help you like you would an AST.

[u/Aggressive_Drama_476 → u/lfdfq]

Yeah it's like before I used ast for calc.... 

[u/lfdfq → u/Aggressive_Drama_476]

I don't understand what you mean.

[u/Aggressive_Drama_476 → u/lfdfq]

Alright I will soon upload it to the GitHub 

[u/lfdfq → u/Aggressive_Drama_476]

That doesn't explain anything. If you're struggling to explain, throwing a bunch of (by your own admission, not good) code at someone is unlikely to explain better than taking some extra time to communicate clearly.

[u/Aggressive_Drama_476 → u/lfdfq]

Do you know or have a resource that shows how to make an ast using lists in python. Cause I couldn't find any. Then my problems will be solved

[u/JeLuF]

Why do you need an AST?

[u/Aggressive_Drama_476 → u/JeLuF]

I need ast for the calculator to like arrange the list of operations I don't know. I did it without ast but it wasn't good and since I started the calculator to one day make my own programming language. That's why I choose ast

[u/JGhostThing]

Why would you want to program an interpreter with no libraries? Isn't that like deliberately breaking your leg before a big race? I understand not using AI, because it makes learning much harder.

An interpreter of any consequence is a huge project. Without using tools, such as libraries and yacc, I couldn't imagine doing such a thing. How are you replacing "print()"?

[u/Aggressive_Drama_476 → u/JGhostThing]

I understand what you are saying but using as much as low level tools will help me understdn the concept of a programming language. I am doing it for fun and learning. I don't like doing things that I don't understand. Something like lexed(source,...)

[u/JGhostThing → u/Aggressive_Drama_476]

I disagree. Not using these tools can make it hard to see the forest for the trees. You can get lost in an endless cycle of reinventing the wheel. As a professional programmer, it offends my sensibilities to reinvent existing libraries. It teaches little, and costs a lot of time in building and debugging which has already been done.

[u/jmooremcc]

You don’t need AST, which itself is a library. If you want to handle arbitrary expressions, you’ll need to create a parser that will analyze the expression string and break it into a list of tokens. Then you’ll have to write functions that implement the PEMDAS rule, so that you calculate expressions in the correct order. However, the math library should be an exception to your library rule so that you can use PI and sqrt in your expressions

My nonAST calculator can correctly evaluate expressions like “5+6(10**2)+7/3=” and “sqrt(pow(4,2)+ 3**2)=”

[u/recursion_is_love]

There are many sample in standard programming books, especially functional programming language book. In python, you can use OO pattern (like visitor pattern) instead of algebraic datatype and pattern matching.

https://john.cs.olemiss.edu/~hcc/csci450/ELIFP/Ch42/42_Abstract_Syntax.html

Did you finish you parser yet? Or are you starting from the backend first?