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b61a439e29
Constrained interfaces require little change to core carp. In rare cases (illustrated in test/interfaces.carp) we need to make our functions slightly more specific. This weakens inference slightly, but in my opinion is a reasonable case of weakness and not a fault of the type system. Exceptional cases that were typed `a-> a` that is, cases that relied on the previous typing errors related to interfaces, as might be expected, no longer work (as is the case for the higher-order use of fmap in examples/functor.carp). Aside from that, nothing changes.
41 lines
1.3 KiB
Plaintext
41 lines
1.3 KiB
Plaintext
(use IO)
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(use Int)
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(use Array)
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(Project.no-echo)
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(definterface fmap (λ [(Ref (λ [a] b)) (f a)] (f b)))
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(defmodule ArrayExtension
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(defn fmap [f a] (Array.endo-map f a))
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(implements fmap ArrayExtension.fmap)
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)
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(deftype (Box a) [x a])
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(defmodule Box
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(defn fmap [f box] (let [new-x (~f @(Box.x &box))]
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(Box.set-x box new-x)))
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(implements fmap Box.fmap))
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(use Box)
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(use ArrayExtension)
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;; TODO: This function currently concretizes to the type of the first (f *) it
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;; receives. Is there a way for us to ensure it remains generic?
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;; N.B. the only reason it worked previously was because it was ill-typed as
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;; (a -> a) which erroneously served as a universal type.
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;(sig higherOrder (Fn [(f a)] (f b)))
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;(defn higherOrder [x] (fmap &Int.inc x))
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(defn main []
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(do
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(println &(str @(Box.x &(fmap &Int.inc (Box.init 100)))))
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(println &(str @(Box.x &(Box.fmap &inc (Box.init 100)))))
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(println &(str &(ArrayExtension.fmap &inc [10 20 30 40 50])))
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(println &(str &(fmap &Int.inc [10 20 30 40 50])))
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(println &(Array.str &(fmap &Int.inc [10 20 30 40 50])))
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(println &(Array.str &(ArrayExtension.fmap &Int.inc [10 20 30 40 50])))
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;(println &(str &(higherOrder (Box.init 999))))
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;(println &(str &(higherOrder [9 99 999 9999])))
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))
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