destructuring.tiny

###############################################################
#
# Test nested patterns and destructuring of lists with
# patterns.
#
###############################################################

# 3 levels deep

[1,[20,[300]]] ~ a::[b::[c::_]::_]::_ then
    println("Match with three levels a={0} b={1} c={2}", a, b, c)

data = [
    [1, [2, 3], 4],
    [2, [3, 3], 4],
    [3, [4, 3], 4],
    [4, [5, 3], 5],
    [5, [6, 3], 5],
    [6, [7, 3], 5]
]

_ = matchlist data
| a :: [ x :: y:: _] :: 4 :: _ ->
    println("1) match a={0} x={1} y={2}", a, x, y)
| a :: [ x :: y:: _] :: 5 :: _ ->
    println("2) match a={0} x={1} y={2}", a, x, y)
| ->
    error 'Default pattern'

###############################################################
#
# Function set to turn a flat list of items into a list of pairs
# using pattern matching and function sets.
#
###############################################################

def pairs []        -> [];
def pairs x::[]     -> [[x, 0]];
def pairs x::y::xs  -> [x, y] :+ pairs(xs);

#
# Now test the functions. They should all print true.
#
alert 'Testing destructuring with patterns; should be all true.';
(pairs([]) == []) |> println;
(pairs([1]) == [[1, 0]]) |> println;
(pairs([1,2]) == [[1, 2]]) |> println;
(pairs([1,2,3]) == [[1, 2], [3, 0]]) |> println;
(pairs([1,2,3,4]) == [[1, 2], [3, 4]]) |> println;
(pairs([1,2,3,4,5]) == [[1, 2], [3, 4], [5, 0]]) |> println;
(pairs([1,2,3,4,5,6]) == [[1, 2], [3, 4], [5, 6]]) |> println;
(pairs([1,2,3,4,5,6,7]) == [[1, 2], [3, 4], [5, 6], [7, 0]]) |> println;

println('All done!')