Haskell, newtype vs data

[deniok]

Сегодня на stackoverflow, отвечая на вопрос, Andreas Hammar привёл хорошие примеры. Сохраняю на будущее, как простые задачки для студентов

data    D a = D a
data    S a = S !a
newtype N a = N a

constD x (D y) = x
constS x (S y) = x
constN x (N y) = x

Какие из следующих вызовов завершат свою работу как Deep Thought, а какие как Earth?

D undefined `seq` 42
S undefined `seq` 42
N undefined `seq` 42
constD 42 undefined
constS 42 undefined
constN 42 undefined

Comments

[deni-ok.livejournal.com]

Although often mistaken for a planet, Earth is in reality the greatest supercomputer of all time, designed by the second greatest supercomputer of all time, Deep Thought, to calculate the Ultimate Question of Life, The Universe and Everything (to which the answer is 42). It was built by the then-thriving custom planet industry of Magrathea to run a ten-million-year program in which organic life would play a major role.

Five minutes before the program was to finish running, Earth was destroyed by the Vogons, allegedly to make way for a hyperspace bypass but in fact to prevent the Ultimate Question being discovered, as it was seen as a threat to the psychiatric industry.

[kurilka.livejournal.com]

а, чот я совсем уже книжку позабыл, сорри

[deni-ok.livejournal.com]

Фильм посмотри, он вполне достоин книжки.

[kurilka.livejournal.com]

Не, мне он как-то не особо понравился в отличие от