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Comment by miloshh | Hacker News Reader

Hmmm... but by the same argument, Ruby is also doing it right, by correctly crashing at runtime (there is no way for a language without a type-system and with redefinable operators to discover the error at compile time).

Somehow the author isn't clear on whether he wants "1 < 2 < 3" to return true or to be rejected; if it's the latter, then most languages get it right (except Python and Matlab, as far as I know).

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I think he's actually quite clear on rejecting it as a syntax error. Ruby isn't doing it right in that it throws a type error: 1 < 2 < 3 becomes lt(lt(1, 2), 3), then lt(true, 3) which doesn't check.

I know nothing about Ruby so I don't know how its operator overloading works, but I think that could be a problem if < was redefined with an a -> a -> a signature, or a -> a -> b with b comparable to a, since in this case you wouldn't get the type error. The proper solution, according to the author, would probably be to simply refuse any expression with more than one < (or any other non-associative operator).

It doesn't seem possible to consistently make "1 < 2 < 3" a syntax error in a language powerful enough to redefine <. (Including Haskell, where you could easily hide the Prelude definition and define your own, also changing the fixity declaration.)

So I guess a fair compromise would be if the default implementation rejects "1 < 2 < 3" at either compile-time or run-time, whichever is possible.

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