Why don't more languages offer flow typing?

Re:Why don't more languages offer flow typing? by dragonwriter on Monday April 04, 2022 @01:56PM (#30909826)

You mean sum types, not union types (TypeScript has union types, your example uses sum types.)

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Re:Why don't more languages offer flow typing? by marcosdumay on Monday April 04, 2022 @04:20PM (#30911513)

An union type is the C attempt to implement something like sum types, that other languages extend a bit to literally implement sum types.

Those two words live on different contexts, as unions are about a memory usage pattern, and sum types are about conceptual software design, but they often go together on the same language feature.

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Re:Why don't more languages offer flow typing? by munificent on Monday April 04, 2022 @04:47PM (#30911766)

> An union type is the C attempt to implement something like sum types

Sum types, unions (in the C sense), and union types are three distinct concepts.

Wikipedia's article confusingly merges the latter two concepts together but they're different thing. TypeScript[1] and Scala[2] have union types, but they have nothing like C's notion of "unsafely reuse the same bits in memory to be interpreted as different things".

[1]: https://www.typescriptlang.org/docs/handbook/2/everyday-type...

[2]: https://dotty.epfl.ch/docs/reference/new-types/union-types.h...

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Re:Why don't more languages offer flow typing? by lambdasquirrel on Tuesday April 05, 2022 @12:59AM (#30915444)

I did mean sum types. Thank you for the correction.

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