-- transpose :: [[a]] -> [[a]]
on transpose(xss)
    script column
        on lambda(_, iCol)
            script row
                on lambda(xs)
                    item iCol of xs
                end lambda
            end script

            map(row, xss)
        end lambda
    end script

    map(column, item 1 of xss)
end transpose


-- TEST
on run

    transpose([[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]])

    --> {{1, 4, 7, 10}, {2, 5, 8, 11}, {3, 6, 9, 12}}
end run


-- GENERIC LIBRARY FUNCTIONS

-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    tell mReturn(f)
        set lng to length of xs
        set lst to {}
        repeat with i from 1 to lng
            set end of lst to lambda(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map

-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
    if class of f is script then
        f
    else
        script
            property lambda : f
        end script
    end if
end mReturn