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Hofstadter Figure-Figure sequences: Difference between revisions
Hofstadter Figure-Figure sequences (view source)
Revision as of 21:57, 1 September 2012
, 11 years ago→{{header|Go}}: second method
(→Using cyclic iterators: replace with simpler and faster code: implicit stuff seem to work better) |
(→{{header|Go}}: second method) |
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Line 542:
task 4: PASS
</pre>
The following defines two mutually recursive generators without caching results. Each generator will end up dragging a tree of closures behind it, but due to the odd nature of the two series' growth pattern, it's still a heck of a lot faster than the above method when producing either series in sequence.
<lang go>package main
import "fmt"
type xint int64
func R() (func() (xint)) {
r, s := xint(0), func() (xint) (nil)
return func() (xint) {
switch {
case r < 1: r = 1
case r < 3: r = 3
default:
if s == nil {
s = S()
s()
}
r += s()
}
if r < 0 { panic("r overflow") }
return r
}
}
func S() (func() (xint)) {
s, r1, r := xint(0), xint(0), func() (xint) (nil)
return func() (xint) {
if s < 2 {
s = 2
} else {
if r == nil {
r = R()
r()
r1 = r()
}
s++
if s > r1 { r1 = r() }
if s == r1 { s++ }
}
if s < 0 { panic("s overflow") }
return s
}
}
func main() {
r, sum := R(), xint(0)
for i := 0; i < 10000000; i++ {
sum += r()
}
fmt.Println(sum)
}</lang>
=={{header|Haskell}}==
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