type Species = string
open System.Web.Caching
open System.Web.Caching
open System.Web.Caching
open System.Windows.Forms
open System.Runtime.CompilerServices
type Location = string
type Time = int

type Observation = Species * Location * Time

let os:Observation list = [("Owl","L1",3); ("Sparrow","L2",4); ("Eagle","L3",5);
               ("Falcon","L2",7); ("Sparrow","L1",9);  ("Eagle","L1",14)]


// ========== EXERCISE 2.1 ==========
let obtainLocation (_,l,_) = l:Location

let obtainSpecies (s,_,_) = s:Species

let rec locationsOf s os =
    match (s, os) with
    | (_,[]) -> []
    | (s, oshead::ostail) when obtainSpecies(oshead) = s -> obtainLocation(oshead) :: locationsOf s ostail
    | (s, oshead::ostail) -> locationsOf s ostail

locationsOf "Eagle" os;;
locationsOf "Sparrow" os;;


// ========== EXERCISE 2.2 ==========
let obtainA (a,_) = a:Species

let rec insert a occ =
    match (a, occ) with
    | (a, []) -> [(a,1)]
    | (a, occhead::occtail) when a = obtainA(occhead) -> let (x, y) = occhead
                                                         (x, y + 1)::occtail
    | (a, occhead::occtail)  -> occhead::insert a occtail;;

// White-box tests...
// Insertion of observation "Sparrow"
let occ0 = insert "Sparrow" [("Owl", 1); ("Eagle", 2)];;
// Incrementation of obseration "Eagle"
let occ1 = insert "Eagle" occ0;;

// Insert observation of "Falcon"
let occ2 = insert "Falcon" occ1;;

// Incremention of observation "Sparrow"
let occ3 = insert "Sparrow" occ2;;


// ========== EXERCISE 2.3 ==========
let rec toCount os =
    match os with
    | [] -> []
    | oshead::ostail -> let (s,l,t) = oshead
                        insert s (toCount ostail);;

// ========== EXERCISE 2.4 ==========
let rec select f intv os =
    let (tLow, tHigh) = intv // splits the interval up in lower and upper bound
    match os with
    | [] -> []
    | oshead::ostail -> let (_,_,t) = oshead // obtains t
                        if tLow <= t && t <= tHigh then f(oshead)::select f intv ostail // if t is within interval then call
                        else select f intv ostail;;                                  // f on the current tuple (oshead)
                                                                                  //and concatenate that with the recursive
                                                                                  // call on the rest of os (ostail).
                                                                                  // Else continue on ostail

// ========== EXERCISE 2.5 ==========

select (fun (s,l,t) -> (s,l)) (4,9) os;;