Algebraic Effects

Ooh, that's going to be cool.

I'm still not really in Algebraic Effects (algeff or AE further), same for the programming world mainstream. Anyway, here I want to discuss the ability to add ae to the language similar to Rust.

Little Glossary

To simplify reading this idea, I'll describe the words used here. The better explanation for algebraic effects I see is from the view of try/catch as these are pretty similar concepts.

To perform an effect is like throw for exceptions -- we pause function execution and waiting for the handler. To handle an effect means "doing something with the data performer passed".

Syntax

At first, what do we need to know is what effects do particular function perform. Effects should not be inferred for raw functions (func), for closures it's okay.

From the view of syntax we need to express effects handling, typing and performing.

The keywords I think pretty to use for ae:

• perform - To perform an effect.
• with - For effects annotations (in func signatures, etc.).
• handle - For blocks that handles effects, much like the match expression.
• effect - Declares a new effect item.

perform syntax

The keyword perform is similar to break expression with a value (optional too, though).

// Let's imagine we are somewhere in a function
{
    if something {
        perform effect1.
    }
}