[Haskell-beginners] Help me improve my code

[Antoine Latter]

On Mon, Aug 29, 2011 at 11:52 PM, Neuman Vong <neuman at twilio.com> wrote:
> Hi Haskell people,
>
> I'm pretty new to Haskell still. There were a bunch of things I didn't
> know how to do in the following script, I'm hoping some people on this
> list can help with. For example, I had trouble returning an ExitCode
> and using getProgName without getting a compile-time type error. I
> feel like I'm doing something wrong with the Text/[Char] conversions
> too. I'd also really appreciate any style tips. Thanks in advance!

What errors are you getting?

>
> {-# LANGUAGE OverloadedStrings #-}
> module Main where
>
> import System (getArgs)
> import System.IO (hPutStrLn, stderr)
> import Data.Text (pack, splitOn, length, isPrefixOf, Text)
> import Prelude hiding (length)
>
> data Rate = Rate Text Text deriving (Show)
>
> findBestPrefix number rates = foldl1 longestPrefix $ matching rates
>    where
>        getLength rate = length $ getPrefix rate
>        getPrefix (Rate prefix _) = prefix
>        getPrice (Rate _ price) = price
>        longestPrefix r1 r2 = if getLength r1 > getLength r2 then r1 else r2
>        matching rates = [ rate | rate <- rates, getPrefix rate
> `isPrefixOf` number ]
>
> makeRates = map $ \line ->
>    let (prefix:rate:_) = splitOn ", " (pack line) in Rate prefix rate
>
> main = getArgs >>= \args ->
>    let findBest number rates = findBestPrefix number $ makeRates rates
>    in case args of
>        (arg:_) -> interact $ (++ "\n") . show . findBest (pack arg) . lines
>        _ -> hPutStrLn stderr "Pass in a number as the first argument"
>
>
> --
> neuman
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