[zvrba]

> [...] how do you find the code that will run when they do fail? You would have to traverse [...]

I work in a .NET world and there many developers have this bad habit of "interface everything", even if it has just 1 concrete implementation; some even do it for DTOs. "Go to implementation" of a method, and you end up in the interface's declaration so you have to jump through additional hoops to get to it. And you're out of luck when the implementation is in another assembly. The IDE _could_ decompile it if it were a direct reference, but it can't find it for you. When you're out of luck, you have to debug and step into it.

But this brings me to dependency injection containers. More powerful ones (e.g., Autofac) can establish hierarchical scopes, where new scopes can (re)define registrations; similar to LISP's dynamically scoped variables. What a service resolves to at run-time depends on the current DI scope hierarchy.

Which brings me to the point: I've realized that effects can be simulated to some degree by injecting an instance of `ISomeEffectHandler` into a class/method and invoking methods on it to cause the effect. How the effect is handled is determined by the current DI registration of `ISomeEffectHandler`, which can be varied dynamically throughout the program.

So instead of writing

    void DoSomething(...) {
        throw SomeException(...);
    }

you establish an error protocol through interface `IErrorConditions` and write

    void DoSomething(IErrorConditions ec, ...) {
        ec.Report(...);
    }

(Alternately, inject it as a class member.) Now, the currently installed implementation of `IErrorConditions` can throw, log, or whatever. I haven't fully pursued this line of though with stuff like `yield`.

[jiggawatts]

The annoyance is that the .NET standard library already does this precise thing, but haphazardly and in far fewer places than ideal.

ILogger and IProgress<T> comes to mind immediately, but IMemoryCache too if you squint at it. It literally just "sets" and "gets" a dictionary of values, which makes it a "state" effect. TimeProvider might be considered an algebraic effect also.

[SkiFire13]

> I work in a .NET world and there many developers have this bad habit of "interface everything", even if it has just 1 concrete implementation

I work on a Java backend that is similar to what you're describing, but Intellij IDEA is smart enough to notice there is exactly one non-test implementation and bring me to its source code.

[vrighter]

not that familiar with java, but in .net when you do this, it is very common for the implementation to be in a separate assembly, part of a different project

[cweld510]

Doesn’t that imply an interface is necessary though, so you can compile (and potentially release) the components separately? I don’t use .net but this sounds quite similar to pulling things into separate crates in Rust or different compilation units in C, which is frequently good practice.

[mystifyingpoi]

Definitely that could imply the necessity of an interface, but often it's simply done, because everyone working in a project blindly follows an already established poor convention.

[vrighter]

by "it's common in the .Net world" I mean that it seems to be an antipattern that's blindly followed. If there's only ever one implementation, it is the interface, imo

[deergomoo]

> you end up in the interface's declaration so you have to jump through additional hoops to get to it

Bit of a tangent, but this really annoys me when I work on TypeScript (which isn't all that often, so maybe there's some trick I'm missing)—clicking through to check out the definition of a library function very often just takes me to a .d.ts file full of type definitions, even if the library is written in TypeScript to begin with.

In an ideal world I probably shouldn't really need to care how a library function is implemented, but the world is far from ideal.