CODEWITHSUNDEEP
haskell
vikingsteve
vikingsteve

Reputation: 40428

Haskell: simple way to read a line containing Int and Float?

I want to read lines from a file that looks like this:

1 2.1
2 2.2
3 2.3

It's a simple an Int and a Float on each line

This is what I came up with, to read each line:

readFoo :: String -> (Int, Float)
readFoo line = (read (splitOn " " line !! 0), read (splitOn " " line !! 1))

Or I also made a datatype, and then the read part is simple.

data Foo = Foo Int Float deriving (Show, Read)
getM (Foo m p) = m
getP (Foo m p) = p

readFoo :: String -> Foo
readFoo line = read $ "Foo " ++ line :: Foo

But there must be a simpler way to do this, right?

Upvotes: 3

Views: 147

Answers (1)

shang
shang

Reputation: 24832

One neat way to express this is using the ViewPatterns extension

{-# LANGUAGE ViewPatterns #-}

readFoo :: String -> (Int, Float)
readFoo (words -> [read -> i, read -> f]) = (i ,f)

Another way to write it in standard Haskell would be e.g.

readFoo :: String -> (Int, Float)
readFoo ln = (read i, read f) where
    [i, f] = words ln

Of course, all this assumes that you don't care about error handling.

Upvotes: 10

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