Re:Sisal: a functional parallel programming language
by gizmo686 on Monday June 27, 2016 @08:27PM
(#11990615)
It would be nice if Haskell could figure out (-) functions; as it is, it always consider things like (- 2) to be a number, not a function (even when only a function would typecheck).
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Re:Sisal: a functional parallel programming language
by prodigal_erik on Tuesday June 28, 2016 @11:47PM
(#11999356)
ML might have had the right idea, using op~ for unary negation and op- for binary subtraction. I definitely would not want parsing to depend on type declarations; that's a slippery slope towards Perl...
Re:Sisal: a functional parallel programming language
by gizmo686 on Wednesday June 29, 2016 @12:06AM
(#11999425)
I suspect that you could do this already using typeclasses. We want (-2) to be a function of the type `Num a => a -> a`, so we could, in theory, make functions of this type an instance of Num.
I do not immediately see this causing problems for correct programs, but it would probably lead to horribly confusing problems in incorrect code, including converting some type errors into runtime errors.
A simpler approach is to say that you can not have a space after the unary "-", so (-2) parses to a numeric literal, and (- 2) parses to a function.