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Today's Topics:
1. How to include {-# LANGUAGE LambdaCase #-} at the ghci
prompt (Galaxy Being)
2. Re: How to include {-# LANGUAGE LambdaCase #-} at the ghci
prompt (Francesco Ariis)
3. Re: How to include {-# LANGUAGE LambdaCase #-} at the ghci
prompt (Galaxy Being)
4. Closure: exact wording (Galaxy Being)
----------------------------------------------------------------------
Message: 1
Date: Fri, 26 Mar 2021 12:20:55 -0500
From: Galaxy Being <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: [Haskell-beginners] How to include {-# LANGUAGE LambdaCase
#-} at the ghci prompt
Message-ID:
<CAFAhFSXg=q4EVK1u+bE0WpkT==dzao2gfy7q-k8mfmhr6hz...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
I've got this code I've entered into the ghci by hand between :{ and :}
:{
{-# LANGUAGE LambdaCase #-}
data List a = Empty | Cons a (List a) deriving (Eq, Ord, Show)
infixr 5 `Cons`
subst_c :: (a -> Bool) -> (a, MyList a) -> MyList a
subst_c pred = \ case
(_, Empty) -> Empty
(n, Cons e t)
| pred e -> Cons n $ subst_c pred (n, t)
| otherwise -> Cons e $ subst_c pred (n, t)
:}
but I keep getting the error
Illegal lambda-case (use -XLambdaCase)
This works fine inside an .hs file and :load and run at the prompt.
However, I'm using Emacs org-mode and need to keep everything limited to a
version of hand-entered :{ ... :}. Any suggestions?
LB
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Message: 2
Date: Fri, 26 Mar 2021 18:31:53 +0100
From: Francesco Ariis <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] How to include {-# LANGUAGE
LambdaCase #-} at the ghci prompt
Message-ID: <20210326173152.GA9876@extensa>
Content-Type: text/plain; charset=utf-8
Il 26 marzo 2021 alle 12:20 Galaxy Being ha scritto:
> I've got this code I've entered into the ghci by hand between :{ and :}
>
> :{
> {-# LANGUAGE LambdaCase #-}
> data List a = Empty | Cons a (List a) deriving (Eq, Ord, Show)
> infixr 5 `Cons`
>
> subst_c :: (a -> Bool) -> (a, MyList a) -> MyList a
> subst_c pred = \ case
> (_, Empty) -> Empty
> (n, Cons e t)
> | pred e -> Cons n $ subst_c pred (n, t)
> | otherwise -> Cons e $ subst_c pred (n, t)
> :}
>
λ> :set -XLambdaCase
------------------------------
Message: 3
Date: Fri, 26 Mar 2021 16:17:19 -0500
From: Galaxy Being <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] How to include {-# LANGUAGE
LambdaCase #-} at the ghci prompt
Message-ID:
<cafahfsupblaloic-xxcvbdfo_czc5cazq1pqyodkp5pgchu...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Exactly. Thanks.
On Fri, Mar 26, 2021 at 12:33 PM Francesco Ariis <[email protected]> wrote:
> Il 26 marzo 2021 alle 12:20 Galaxy Being ha scritto:
> > I've got this code I've entered into the ghci by hand between :{ and :}
> >
> > :{
> > {-# LANGUAGE LambdaCase #-}
> > data List a = Empty | Cons a (List a) deriving (Eq, Ord, Show)
> > infixr 5 `Cons`
> >
> > subst_c :: (a -> Bool) -> (a, MyList a) -> MyList a
> > subst_c pred = \ case
> > (_, Empty) -> Empty
> > (n, Cons e t)
> > | pred e -> Cons n $ subst_c pred (n, t)
> > | otherwise -> Cons e $ subst_c pred (n, t)
> > :}
> >
>
> λ> :set -XLambdaCase
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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Message: 4
Date: Fri, 26 Mar 2021 16:32:01 -0500
From: Galaxy Being <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: [Haskell-beginners] Closure: exact wording
Message-ID:
<CAFAhFSWXUBhncwiOQrGZF5=eaz5rfns_hyc1mdyyegrptap...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
I've got this
addTwo x y = x + y
aT5 = addTwo 5
> aT5 3
8
Is it right to say aT5 is a closure over 5, or a closure over addTwo 5?
LB
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