Functional Programming: This thread is like a burrito

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > Functional Programming: This thread is like a burrito

KaneTW: Dec 2, 2011

Yay! A FP thread.

http://www.seas.upenn.edu/~cis194/spring13/lectures.html is probably the best Haskell beginner resource (probably above books) (I can't really recommend LYAH, but RWH is good (but not as good as CIS194)).

https://github.com/bitemyapp/learnhaskell should be in the OP too.

# ¿ May 1, 2015 01:06

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# ¿ Apr 28, 2024 13:16

KaneTW: Dec 2, 2011

When you update GHC it creates a new cabal tree for the new version. You'll have to reinstall what you need and recompile existing binaries if they depend on runtime linking like Xmonad. I usually keep the old version around for a while.

# ¿ Jun 14, 2015 21:51

KaneTW: Dec 2, 2011

https://github.com/bitemyapp/learnhaskell

# ¿ Jun 19, 2015 09:29

KaneTW: Dec 2, 2011

I can't think of anything better than

code:

instance Show Day where
  show Mon = "Monday"
   ...

. The solution using indexing is rather ugly and not really Haskelly.

I wouldn't derive Enum because

code:

> succ Sun
*** Exception: succ{Day}: tried to take `succ' of last tag in enumeration

makes no sense.

# ¿ Sep 17, 2015 02:15

KaneTW: Dec 2, 2011

GHC 8.0 release candidate is around the corner, including cool stuff like -XTypeInType (blog post about it), Strict Haskell, Duplicate Record Fields (allows you to have record field names where the ambiguity is resolved during typechecking) and a whole lot of other stuff.

# ¿ Dec 19, 2015 14:26

KaneTW: Dec 2, 2011

Visible type application might make it into GHC 8.0, allowing you to write things like

code:

:t length
length :: Foldable t => t a -> Int
:t length @[]
length :: [a] -> Int

or a more useful example,

code:

:t read
read :: Read a => String -> a
:t read @Int
read :: String -> Int

This is especially nice whenever you used to need a proxy type or similar to disambiguate typevars.

# ¿ Dec 22, 2015 05:04

KaneTW: Dec 2, 2011

What GHC does is rename the type variables so things like that Elm error are obvious.

code:

module Error where

const' :: a -> b -> b
const' _ x = x'
  where
    x' :: b
    x' = x

code:

Error.hs:7:10: error:
    � Couldn't match expected type �b1� with actual type �b�
      �b� is a rigid type variable bound by
        the type signature for:
          const' :: forall a b. a -> b -> b
        at Error.hs:3:11
      �b1� is a rigid type variable bound by
        the type signature for:
          x' :: forall b1. b1
        at Error.hs:6:11
    � In the expression: x
      In an equation for �x'�: x' = x
    � Relevant bindings include
        x' :: b1 (bound at Error.hs:7:5)
        x :: b (bound at Error.hs:4:10)
        const' :: a -> b -> b (bound at Error.hs:4:1)

# ¿ Jan 1, 2016 15:51

KaneTW: Dec 2, 2011

It's a good book. Certainly way better than the books I used when I learned Haskell.

# ¿ Jan 1, 2016 17:31

KaneTW: Dec 2, 2011

That buildwrapper error seems like a bug in the module or its version bounds. Building stuff with C libraries is a gigantic pain on Windows.

Leksah starts and editing works fine, but I can't get it to (didn't bother too much) actually build packages, so I just keep a MSYS shell open and build with stack.

http://darcs.net/Windows has steps on how to build libcurl bindings and you adapt those for zlib/cairo, but honestly it's not worth the trouble. Boot up a Linux VM and call it a day.

Alternatively, you can try getting Emacs or something to work. Probably better chance since you can build ghc-mod etc. easily on Windows.

# ¿ Mar 14, 2016 23:29

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# ¿ Apr 28, 2024 13:16

KaneTW: Dec 2, 2011

"lucky is a function from any Integral type to String" sounds good to me. Maybe "from any type that's an instance of Integral to String" but while a bit more accurate it's also a mouthful

# ¿ Mar 21, 2016 02:58

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