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The original was posted on /r/programminglanguages by /u/aerosayan on 2023-12-14 11:55:51.

Hello, this is somewhat of an open ended question, and I’m not sure how to ask it correctly, but how do you ensure that the rules of your language are correct?

I don’t think there’s a correct answer, other than “try to make it correct”, but since there’s not books on this kind of logical reasoning, I think asking other experienced folks will be educational.

For example,

It’s hard to explain what I mean by “rules” I’m referring to, but here’s an example …

I want to implement refrences/pointers in my language, but since I want to compile down to Fortran, I can’t use pointers, since they cause aliasing, and limit optimization possibilities, specifically in Fortran.

So I just came up with the idea that references/pointers will just be implemented as integer indexes to arrays.

i.e if there’s a large array of cells, we just get the cell at index i, and everywhere the pointer is used, the compiler will substitute it for array_of_cells[i].

This was nice until I realized that I need strict rules for ensuring correctness , like …

  1. Reference once set, can not be changed within that scope.
  2. Reference to a local object can not be returned from a function, since the local object will go out of scope and will be deallocated automatically.
  3. Reference can only be created for objects that are in scope, and unlike C/C++, they can not refer to anywhere random in memory. We need a specific target, and the target can not change.

These are just 3 example rules, but I think I will need hundred more rules like this to ensure proper correctness of the language.

I have to do the work myself, but how do we ensure that we’re not missing something?

Is it just logical reasoning, or is there a framework for inventing/discovering these rules?

I think reading standards of other languages will help, but I don’t have experience in that, because they seem complicated. Although I’m trying to study C and Fortran’s standards because I need them.

Thanks.