Add static variables
rozaxe opened this issue · comments
⭐️ Proposed change
I propose a way to define instance variables which can be called on the type rather on an instance of the type.
🤔 Rationale
This would allows to store values on a type, and use them from type methods.
This would also allows the development of the singleton pattern.
🕺Example
Here an example of an implementation of the singleton pattern :
🐇💾🍇
🐇🖍🆕 instance 🍬💾
🔐🆕🍇🍉
🐇❗️🐾 ➡️ 💾 🍇
↪️🤷♂️ 🙌 instance 🍇
🆕💾🆕❗️ ➡️ 🐇🖍instance
🍉
↩️ 🍺instance
🍉
🍉
This defines a static variable 🐇🖍🆕 instance 🍬💾 accessibles from the type itself with 🐇instance.
We can then call the singleton with 🐾🐇💾❗️ and access the unique instance of the type 💾
Perfect except that I don't think ➡️🐇🖍instance is good. ➡️🖍instance like with instance methods would be better. After all, type methods really are in the context of the type. (🐕 contains the type.)
You wanna try to implement this? 🙂
At least I will try ! 😁
I am digging into implementing this, and I found a problem. How a static variable initial value would be set ?
🐇 🐟 🍇
🐇🖍🆕 count 🔡
🐇 ❗️ 🙇♀️ 🍇
count ➕ 1 ➡️ 🖍 count
🍉
🐇 ❗️ 💁♂️ 🍇
😀 count ❗️
🍉
🍉
For example, what would be count initial value ?
Do you think we could add "on step declaration and assignment variable" in type as well ?
Something like that :
🐇 👩💼 🍇
5300 ➡️ 🖍🆕 money
🆕 🍇🍉
🍉
After calling 🆕👩💼🆕 the value of money would be set to 5300 ?
Thus, we could write something like that for static variables :
🐇 🐟 🍇
0 ➡️ 🐇🖍🆕 count
🍉
Declaring and Assigning in one step in types would be great.
These expressions would have to be evaluated in a context where 🐕 (and thus access to instance variables) is disallowed, I guess.
@rozaxe Can you please give me a heads-up before you implement anything concerning the declaration and assignment in type bodies? I want to some refactoring here first, if possible.
No problem, go again ! (I need some time to understand how the compile works in whole, so do not hesitate to implements features)
So we have a syntax issue here. Consider this code:
🐇 👩💼 🍇
🆕🦍🆕❗️ ➡️ 🖍🆕 pet
🍉
While this is a variable assignment, it is hard for the compiler to tell it apart from an initializer definition:
🐇 👩💼 🍇
🆕🦍 🍇
🍉
🍉
Emojicode uses a strict LL(1) grammar, which makes this impossible. I think the best solution is:
🐇 👩💼 🍇
🖍🆕 pet ⬅️ 🆕🦍🆕 ❗️
🍉
So for recap, for instance variable :
🖍🆕 pet ⬅️ 🆕🦍🆕 ❗️
And for "in method variable" :
🆕🦍🆕 ❗️➡️ 🖍🆕 pet
Yes, although I think it might even be
🖍🆕 pet 🦍 ⬅️ 🆕🦍🆕 ❗️
because type inference could be difficult here. Furthermore, a well-reasoned argument against something like this was made in #83 .
✅ This is implemented on 0.7.
https://0-7.emojicode.org/docs/reference/classes-valuetypes.html#instance-variables
Sorry, I do not feel I will be able to implement this (too many knowledge).
I will keep my motivation for implementing some useful package !