i’ve read
http://weblog.raganwald.com/2007/02/guest-blogger-tom-moertel-derives-y.html
and finally figured out this:
a trick to make currying easier
class Proc
def -@
self.curry
end
end
def Y &f
g = → h, x, *xs { f[h[h], x, *xs] }
g[g]
end
and had a try:
factorial = Y {|f, n| n == 0 ? 1 : f[n - 1] * n}
puts factorial[12]
=> 479001600
fibbonaci = Y {|f, n| n <= 2 ? 1 : f[n - 1] + f[n - 2]}
puts fibbonaci[10]
=> 55
the intresting part is:
if you replace “x, *xs”(like pattern matching in functional languages
^_^) with “*args”, it overflows the stack.