type car = string*string*int

let car1 = ("Opel", "astra", 1999)
let car2 = ("Renault", "megane", 2004)
let car3 = ("Opel", "corsa", 2009)
let car4 = ("Nissan", "micra", 2004)
let car5 = ("Opel", "corsa", 2009)
let car6 = ("Nissan", "micra", 2004)

let carList = [car1;car2;car3;car4;car5;car6]

let apperiance cars productionYear =
	let rec countApperiance filteredCars result =
		match filteredCars with
		| [] -> result
		|	(cars1,cars2,cars3)::t ->
			let rec countAndRemove currentCars resultCars (x1,x2,x3) count =
				match currentCars with
				| [] -> (resultCars, count)
				| (h1,h2,h3)::t -> if(h1=x1 && h2=x2) then countAndRemove t resultCars (x1,x2,x3) (count+1)
													else countAndRemove t ((h1,h2,h3)::resultCars) (x1,x2,x3) count
				in let (l1,a1) = countAndRemove filteredCars [] (cars1,cars2,cars3) 0
					in countApperiance l1 ((cars1,(cars2,a1))::result)

	in countApperiance (List.filter (function (x,y,z)->z==productionYear) cars) [];;

apperiance carList 2004;;