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Today's Topics:
1. Pattern matching over functions (Giacomo Tesio)
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Message: 1
Date: Wed, 7 Dec 2011 11:34:28 +0100
From: Giacomo Tesio <[email protected]>
Subject: [Haskell-beginners] Pattern matching over functions
To: [email protected]
Message-ID:
<cahl7psehyijccyaytga5nn4rx6vnenu-juslewl+xkzrzxu...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi Haskellers,
I'm wondering why, given that functions and referential transparency are
first class citizens in haskell, it isn't possible to write a mapping
function this way:
f1 :: a -> b
f2 :: a -> b
f3 :: c -> a -> b
map :: (a -> b) -> T a -> T b
map f1 = anEquivalentOfF1InTCategory
map f2 = anEquivalentOfF2InTCategory
map f3 $ c = anEquivalentOfF3withCInTCategory
map unknown = aGenericMapInTCategory
Is it "just" the implementation complexity of the feature in ghc that
prevents this?
Or is it "conceptually" wrong?
At a first look, I thought that most of complexity here should be related
to function's equality, but than I thought that the function full name
should uniquely map from the category of meanings in the programmer mind to
the category of implementations available to the compiler's.
Giacomo
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