You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
32 lines
707 B
32 lines
707 B
-- function closures are powerful
|
|
|
|
-- traditional fixed-point operator from functional programming
|
|
Y = function (g)
|
|
local a = function (f) return f(f) end
|
|
return a(function (f)
|
|
return g(function (x)
|
|
local c=f(f)
|
|
return c(x)
|
|
end)
|
|
end)
|
|
end
|
|
|
|
|
|
-- factorial without recursion
|
|
F = function (f)
|
|
return function (n)
|
|
if n == 0 then return 1
|
|
else return n*f(n-1) end
|
|
end
|
|
end
|
|
|
|
factorial = Y(F) -- factorial is the fixed point of F
|
|
|
|
-- now test it
|
|
function test(x)
|
|
io.write(x,"! = ",factorial(x),"\n")
|
|
end
|
|
|
|
for n=0,16 do
|
|
test(n)
|
|
end
|