euler4.opa

function is_palindrome(int number){
    word = Int.to_string(number)
    word == String.reverse(word)
}

function pair_with(int elem, it){
    Iter.map(function(el){ (elem, el) }, it)
}

function pairs(seq){
    match(seq.next()){ 
      case {none} : {  next : function () { none } }
      case {some:it} : Iter.append(pair_with(it.f1, it.f2), pairs(it.f2)) 
    }
}

before = Date.now()

nums = Iter.init(999, function(int elm){ elm - 1 }, function(int elm){ elm > 100 })

combs = pairs(nums)

products = Iter.map(function(pair) { pair.f1 * pair.f2 }, combs)

palindrome_products = Iter.filter(function(num){ is_palindrome(num) }, products)

jlog(Int.to_string(Option.get(Iter.max(palindrome_products))))

//jlog(Int.to_string(Option.get(palindrome_products.next()).f1))


after = Date.now()

duration = Duration.in_milliseconds(Duration.between(before, after))

jlog(Int.to_string(duration))