chapter 4 confusion

Hello,

Chapter 4 of RealWorldOcaml begins with this programm :

open Core.Std

let build_counts () =

In_channel.fold_lines stdin
~init:[] ~f:(fun
counts line ->

let count =

match List.Assoc.find
counts line with

| None -> 0

| Some x
-> x

in List.Assoc.add counts line (count +
1) )

let () =
build_counts ()

|>
List.sort ~cmp:(fun (_,x) (_,y) -> Int.descending
x y)

|>
(fun l
-> List.take
l 10)

|>
List.iter ~f:(fun (line,count)
-> printf "%3d:
%s\n" count line)

But I do not really understand what each line does

1) What means ln.channel.fold_lines stdin ~init part means ?

2) What does the |> does exactly. I know chapter 2 does explain
it a little bit but it's still not clear to me

3) What does ~cmp mean.

Roelof

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Posted by: Roelof Wobben <[email protected]>
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