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0 pointscaspper691y ago0 comments

Having reviewed the proposal (of course no guarantee that's what discriminated unions (aka product types aka algebraic data types) will look like), and it appears that it very much integrates nicely with the language.

I don't suspect they'll make too many changes (if any) to the existing standard library itself, but rather will put functions into their own sub-namespace moving forward like they did with concurrent containers and the like.

Given their penchant for backwards compatibility, I think old code is safe. Will it create a schism? In some codebases, sure. Folks always want to eat the freshest meat. But if they do it in a non-obtrusive way, it could integrate nicely. It reminds me of tuples, which had a similar expansion of capabilities, but the integration went pretty well.

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tubthumper81y ago

>that's what discriminated unions (aka product types aka algebraic data types)

Just an FYI, discriminated unions are not product types, they are sum types. It's named so because the total number of possibilities is the sum of the number of possibilities for each variant.

Ex. A sum type Color is a PrimaryColor (Red, Blue, Yellow) OR a SecondaryColor (Purple, Green, Orange), the total number of possibilities is 3 + 3 = 6.

For a product type, if a ColorPair is a PrimaryColor AND a SecondaryColor, the total number of possibilities is 3 * 3 = 9

Both sum types and product types are algebraic types, in the same way that algebra includes both sums and products.

For the standard library, I'm curious for the family of TryParse kind of functions, since those are well modeled by a sum type. Maybe adding an overload without an `out` argument would give you back a DU to `switch` on

caspper69OP1y ago

I make that mistake more often than I care to, but you are 100% spot-on. They are sum types, not product types. Thank you for making me walk the walk of shame!

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