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Today's Topics:
1. Re: First code review (Erik de Castro Lopo)
2. Mutable variables in do block? (Emanuel Koczwara)
3. Re: Mutable variables in do block? (Ozgur Akgun)
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Message: 1
Date: Sun, 24 Feb 2013 18:29:22 +1100
From: Erik de Castro Lopo <[email protected]>
Subject: Re: [Haskell-beginners] First code review
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=US-ASCII
Brent Yorgey wrote:
> Since both the Grid and Heuristic values are created once and
> then used in a read-only fasion, this is a perfect opportunity to use
> arrays: see
>
>
> http://hackage.haskell.org/packages/archive/array/latest/doc/html/Data-Array.html
>
> Using read-only arrays is really quite simple (as opposed to
> read/write arrays which require a monad of some sort).
Brent, out of curiosity, why Array instead of Data.Vector?
Cheers,
Erik
--
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/
------------------------------
Message: 2
Date: Sun, 24 Feb 2013 11:41:00 +0100
From: Emanuel Koczwara <[email protected]>
Subject: [Haskell-beginners] Mutable variables in do block?
To: [email protected]
Message-ID: <1361702460.3205.32.camel@emanuel-Dell-System-Vostro-3750>
Content-Type: text/plain; charset="UTF-8"
Hi,
1 main = do
2 line <- getLine
3 putStrLn line
4 line <- getLine
5 putStrLn line
Here I have 'line' first bounded with a value at line 2, and then at
line 4. It looks like I can set (or bind) a variable in 'do' block more
than once, and it looks like it's a destructive update.
But as I'm thinking about this more and more, it appears that the first
and second 'line' are just an ordinary immutable variables. Line 4 just
hides the 'line' from line 2 (outer lambda). Am I right?
Emanuel
------------------------------
Message: 3
Date: Sun, 24 Feb 2013 10:44:59 +0000
From: Ozgur Akgun <[email protected]>
Subject: Re: [Haskell-beginners] Mutable variables in do block?
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Message-ID:
<calzazpb6t7ues-hmug6mmer_k4zohurhppseotj8uyp3l2r...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi,
On 24 February 2013 10:41, Emanuel Koczwara <[email protected]>wrote:
> it appears that the first
> and second 'line' are just an ordinary immutable variables. Line 4 just
> hides the 'line' from line 2 (outer lambda). Am I right?
>
Exactly. You can try desugaring the do notation to see what's going on even
more clearly.
Best,
Ozgur
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