count chars in a file

charscounter.scala

// see also http://piyush.purang.net/blog/Reading_Type_Signatures_5e999531-595f-4348-b44c-e239be962885

import java.io.File
// following is the goal
type CountCharsInAFile = String => Int

type PathToFile = String => File 
def pathToFile : PathToFile = new File(_) 

type FileToLines = File => List[String]
def fileToLines: FileToLines = io.Source.fromFile(_).getLines.to[List]

type CountCharsInLines = List[String] => List[Int]  // we can decompose this further into type CountCharsInALine = String => Int 
def countCharsInLines: CountCharsInLines = x => x.map(y => y.to[List].length+1)  // the +1 counts line break chars that `getLines` above looses. Will fail if two chars represent a line break.

type Total = List[Int] => Int
def total: Total = _.sum

//bring the parts together
def countCharsInAFile: CountCharsInAFile = (total compose countCharsInLines compose fileToLines compose pathToFile)(_)
// or alternatively
def countCharsInAFile2: CountCharsInAFile = x => total(countCharsInLines(fileToLines(pathToFile(x)))) // hmm '_' instead of 'x' didn't work under 2.11.1

//use them
countCharsInAFile("somechars.txt")
countCharsInAFile2("somechars.txt")