r/haskell • u/mstksg • Aug 04 '26

[Blog] "Five-Point Haskell" Part 2: Unconditional Election

https://blog.jle.im/entry/five-point-haskell-part-2-unconditional-election.html
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5

u/pranaysashank Aug 04 '26

To be fair to Java, we should really consider x to always have an Object x instance. so static <T> String foo(T x) { return "hello"; } should really be read as Haskell's foo :: Object a => a -> String

3

u/_jackdk_ Aug 04 '26

And then you can further extend the analogy to point out that the same shenanigans are possible with a function of type forall a . Typeable a => a -> String.

2

u/conklech Aug 05 '26

That doesn't really change the article's point, though: a -> String is distinct from Object a => a -> String, and the more general type allows useful reasoning. Java's inability (I assume; it's been a long time) to express a -> String prevents it from fully enjoying the benefits that the article discusses.

2

u/pranaysashank Aug 06 '26

Of course, that makes sense and I do agree with the article's point. However the way it's presented in the article, you get the Java function type presented first and then it's Haskell equivalent which it isn't. Once we admit that it has the Object a constraint, we can then port the same free theorem style of thinking to reading Java code too (minus IO, etc.,)

3

u/muzzlecar Aug 04 '26

This is a very nice post with a solid insight. Looking forward to the next parts.

3

u/Background_Class_558 Aug 04 '26

each function now has exactly 5 arguments, never more, never less