December 2013 - Beginners

download latest version of cabal-install from hackage
by harry 10 Dec '13

10 Dec '13

I'm trying to write a script that will download and install the latest version of cabal-install. However, I can't find a URL to automatically fetch the latest version. How can this be done?

2 3

How can I read package document?
by S. H. Aegis 08 Dec '13

08 Dec '13

Hi. I'm new to Haskell. I installed Palindromes package through cabal. But I don't know the usage of command. (Not enough information on Home Page.) How can I read document? Thank you. =)

3 4

Overflow when reading C types
by Patrick Redmond 02 Dec '13

02 Dec '13

Prelude> import Foreign.C.Types Prelude Foreign.C.Types> read "-10" :: CUInt 4294967286 Prelude Foreign.C.Types> read "300" :: CChar 44 This seems like a bug. Shouldn't these result in some kind of read error? The values expressed as strings are simply not part of the type they are being parsed into. However, Haskell seems to parse them into an arbitrarily wide numeric type, and then overflow them down to the correct size. What's the rationale here?

5 7

Understanding inheritance
by Patrick Browne 02 Dec '13

02 Dec '13

3 2

How to save a bracket in this case?
by yi lu 02 Dec '13

02 Dec '13

Hi, I want to calculate *(81/10)^2*. However, after I typed *81/10*, I remembered to add a bracket to surround *81/10*. Is there one way to do some trick to save this bracket? Actually I can *Ctrl+A* to move to the first character of this line. I want the other solution. Yi

2 1

This code does not work : conversion error
by willie ekaputra 01 Dec '13

01 Dec '13

Hi everyone ! I am newbie and I made this code for counting k, so that 2^k divisor of n.Somehow it doesn't work. Anyone knows what is wrong? Regards and thanks. Wili. maxexp2:: Int -> Int maxexp2 n |n== 0 || 2^k 'mod' n /=0 =0 |otherwise = k Where k= e ' div' f e=round (fromIntegral (log n)) f = round (fromIntegral (log 2))

4 3

Equality instance for lists
by Patrick Browne 01 Dec '13

01 Dec '13

3 3