groupBy.bat

::#! 2>/dev/null || echo "
@echo off
call scala -savecompiled %~f0 %*
goto :eof
" >//null 
#!/bin/sh
exec scala -savecompiled "$0" "$@"
::!#

args match {
  case Array(lineRegex) => // OK
  case Array(lineRegex, "sum") => // OK
  case Array(lineRegex, "avg") => // OK
  case Array(lineRegex, "min") => // OK
  case Array(lineRegex, "max") => // OK
  case _ => {
    println("""
      | Group and count/sum/avg/min/max lines based on a given regex.
      | Grouping is done by the first group of the regex, summing etc by the second group.

      | Usage:
      |   groupBy "<regex>"
      |   groupBy "<regex>" sum
      |   groupBy "<regex>" avg
      |   groupBy "<regex>" min
      |   groupBy "<regex>" max

      | Examples:
      |   (echo a1 && echo b2 && echo a3) | groupBy "([a-z])\d"
      |     'a' 2
      |     'b' 1

      |   (echo a1 && echo b2 && echo a3) | groupBy "([a-z])(\d).*" sum
      |     'a' 4.0
      |     'b' 2.0

      |   (echo a1 && echo b2 && echo a3) | groupBy "([a-z])(\d).*" avg
      |     'a' 2.0
      |     'b' 2.0

      |   (echo a1 && echo b2 && echo a3) | groupBy "([a-z])(\d).*" min
      |     'a' 1.0
      |     'b' 2.0

      |   (echo a1 && echo b2 && echo a3) | groupBy "([a-z])(\d).*" max
      |     'a' 3.0
      |     'b' 2.0
    """.stripMargin)
    exit
  }
}

import scala.io._

val lines = Source.stdin.getLines.toSeq

val GroupByPattern = args(0).r
val method = if (args.length == 1) None else Some(args(1))

lines groupBy { x => (for (m <- GroupByPattern.findFirstMatchIn(x)) yield m.group(1)).mkString } foreach { case (key, values) => println("'" + key + "' " + (method match {
	case Some("sum") => values.map { case GroupByPattern(a,b) => b.toDouble }.sum
  case Some("avg") => values.map { case GroupByPattern(a,b) => b.toDouble }.sum / values.size
  case Some("min") => values.map { case GroupByPattern(a,b) => b.toDouble }.min
  case Some("max") => values.map { case GroupByPattern(a,b) => b.toDouble }.max
	case None => values.size
}))}