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On top of your answer and the other, I still think Discriminated Unions are still a big hole in c#. I know they are supposedly working on it, but until they off

On top of your answer and the other, I still think Discriminated Unions are still a big hole in c#. I know they are supposedly working on it, but until they officially release it I'm not believing them.

keithnz 3y ago
It's easy enough to do DUs, they are working on it, but they are just syntactic sugar for abstract class/subclass for instance, as an example for this https://fsharpforfunandprofit.com/posts/designing-for-correctness/ https://fsharpforfunandprofit.com/posts/designing-for-correc... where a C# solution is suggested and done with DUs in F#, I wrote the equivalent DU solution in C#... https://gist.github.com/keithn/ceeeed5f7eb567e1b2333747065d10dd https://gist.github.com/keithn/ceeeed5f7eb567e1b2333747065d1... Only thing you don't have is exhaustive checking, which I personally don't think is much of a problem pragmatically.
- runevault 3y ago
  Exhaustive checking and locking down the base type if you don't want anyone else to extend it beyond your choices of subtypes, unless there's a way I don't know about to lock down extending to inside your binary while letting others ask for any types that references it. There's a secondary benefit though if they allow DUs of Structs where you can have it be on the stack as a single value based on the size of the largest subtype that could be incredibly useful when you are worried about performance. Inheritance does not do that.
ericsink 3y ago
I too miss discriminated unions in C#. But even more often, I find myself wishing C# blocks were expressions. In F#, I could do this: let x = let z = whatever ... value and z is inside a local scope. So in C#, I want to do: var x = { var z = whatever; ... value }; Maybe it's just me.
- WorldMaker 3y ago
  I'm finding switch expressions filling that gap a lot lately. I've also picked up at some point a bad habit in "borrowing" JS' ugly IIFE pattern in C#. var x = (() => { var z = whatever; ... return value; })(); It is not the most performant way to write that code and if the contents start to get long, refactoring to its own method starts to feel more likely, but in one-off cases, it seems fine for how ugly it is.
- runevault 3y ago
  Nah it isn't just you. I probably use this more in my Rust experience then F# but when I remember it is there it is incredibly valuable.

keithnz 3y ago

It's easy enough to do DUs, they are working on it, but they are just syntactic sugar for abstract class/subclass for instance, as an example for this https://fsharpforfunandprofit.com/posts/designing-for-correctness/ https://fsharpforfunandprofit.com/posts/designing-for-correc... where a C# solution is suggested and done with DUs in F#, I wrote the equivalent DU solution in C#... https://gist.github.com/keithn/ceeeed5f7eb567e1b2333747065d10dd https://gist.github.com/keithn/ceeeed5f7eb567e1b2333747065d1... Only thing you don't have is exhaustive checking, which I personally don't think is much of a problem pragmatically.

runevault 3y ago
Exhaustive checking and locking down the base type if you don't want anyone else to extend it beyond your choices of subtypes, unless there's a way I don't know about to lock down extending to inside your binary while letting others ask for any types that references it. There's a secondary benefit though if they allow DUs of Structs where you can have it be on the stack as a single value based on the size of the largest subtype that could be incredibly useful when you are worried about performance. Inheritance does not do that.

ericsink 3y ago

I too miss discriminated unions in C#. But even more often, I find myself wishing C# blocks were expressions. In F#, I could do this: let x = let z = whatever ... value and z is inside a local scope. So in C#, I want to do: var x = { var z = whatever; ... value }; Maybe it's just me.

WorldMaker 3y ago
I'm finding switch expressions filling that gap a lot lately. I've also picked up at some point a bad habit in "borrowing" JS' ugly IIFE pattern in C#. var x = (() => { var z = whatever; ... return value; })(); It is not the most performant way to write that code and if the contents start to get long, refactoring to its own method starts to feel more likely, but in one-off cases, it seems fine for how ugly it is.
runevault 3y ago
Nah it isn't just you. I probably use this more in my Rust experience then F# but when I remember it is there it is incredibly valuable.