Implementing a very simple 'Wine Rating System' in Haskell

Posted by Alex N on Stack Overflow See other posts from Stack Overflow or by Alex N
Published on 2010-05-08T15:59:27Z Indexed on 2010/05/08 16:08 UTC
Read the original article Hit count: 218

Filed under:

haskell

|

lists

|

tuples

Hello, I have just started learning Haskell and have got stumped on how to add a rating to a custom data type.

The data type I'm using has a name, a year and a tuple (userName and their rating), it looks like:

data Wine = Wine String Int [Rating] deriving (Eq,Ord,Show,Read)
type Rating = (String, Int)

I wanted to allow a user to rate a given wine from a database, stored as [Wine] but cant figure out how to to it. Any pointers or suggestions would be greatly appreciated! Thanks.

© Stack Overflow or respective owner

Related posts about haskell

Learning Haskell: How to remove an item from a List in Haskell

as seen on Stack Overflow - Search for 'Stack Overflow'
Trying to learn Haskell. I am trying to write a simple function to remove a number from a list without using built-in function (delete...I think). For the sake of simplicity, let's assume that the input parameter is an Integer and the list is an Integer list. Here is the code I have, Please tell me… >>> More
Using Data.Heap in Haskell, or reading Haskell docs for a beginner

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to use Haskells Data.Heap module, but I'm incapable of even using it with integers. The only heap I've been capable of using is "empty", which does not take any arguments. Later on I'll figure out how to instance for my needs, but for now I'd be glad if I was even able to test it with… >>> More
What kind of things are easy in Haskell and hard in Scala, and vice versa?

as seen on Programmers - Search for 'Programmers'
There has been some intermingling of Scala and Haskell communities, and I have noticed now and then people commenting on stuff that's supposed to be easy in Haskell and hard and Scala. Less often (maybe because I read Scala questions, not Haskell ones), I see someone mentioning that something in Scala… >>> More
Haskell's cabal dependency problem with happy

as seen on Programmers - Search for 'Programmers'
I have problems installing ghc-mod on my linux machine. cabal worries about "happy" not being available in versione = 1.17: $ cabal install ghc-mod Resolving dependencies... [1 of 1] Compiling Main ( /tmp/haskell-src-exts-1.14.0-1357/haskell-src-exts-1.14.0/Setup.hs, /tmp/haskell-src-exts-1… >>> More
Understanding Haskell's fibonacci

as seen on Stack Overflow - Search for 'Stack Overflow'
fibs :: [Int] fibs = 0 : 1 : [ a + b | (a, b) <- zip fibs (tail fibs)] This generates the Fibonacci sequence. I understand the behaviour of the guards, of :, zip and tail, but I don't understand <-. What is it doing here? >>> More

Related posts about lists

Global Address List, Multiple All Address Lists in CN=Address Lists Container

as seen on Server Fault - Search for 'Server Fault'
When my colleges (that was way before my time here) updated Exchange 2000 to 2003 a English All Address Lists appeared in addition to the German variant. The English All Address Lists have German titled GAL below it. This has just been a cosmetic problem for the last few years. Now as we are in the… >>> More
Lists inside lists don't validate with w3c?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi everybody, I've got some lists inside lists to make some fancy drop-down menus. e.g <ul> <li>something <ul> <li>sub menu</li> </ul> </li> </ul> Problem is, w3c doesn't like it. Is there a way to make this validate… >>> More
Why are listener lists Lists?

as seen on Stack Overflow - Search for 'Stack Overflow'
Why are listener lists (e.g. in Java those that use addXxxListener() and removeXxxListener() to register and unregister listeners) called lists, and usually implemented as Lists? Wouldn't a Set be a better fit, since in the case of listeners there's No matter in which order they get called (although… >>> More
Updating Lists of Lists in Tapestry4 using textfields and a single submit button

as seen on Stack Overflow - Search for 'Stack Overflow'
In Tapestry 4 I am trying it iterate over a list of lists (technically a list of objects who have a list of strings as a data field). I am currently doing this by using 'nested' for components. (This is pseudo code) <span jwcid="Form"> <span jwcid="@For" source="ognl:Javaclass.TopLevelList"… >>> More
jQuery.each for lists and non-lists

as seen on Stack Overflow - Search for 'Stack Overflow'
I've a jQuery.each(data, foo), where data is either a string or a list of strings. I'd like to know if there's an existing utility function to convert the string to a list, or otherwise perform foo on just the string. So instead of the easy route: if (!$.isArray(data)) { foo(0, data); // can't… >>> More