多段階選抜 (Falcon/Scheme)


|多段階選抜|解答日|シリーズ:yieldの練習/ジェネレータを入れ子に/整数平方根・立方根の実装|
|:--|:--|:--|
|問題|　|http://nabetani.sakura.ne.jp/hena/ord24eliseq/<br>https://qiita.com/Nabetani/items/1c83005a854d2c6cbb69|
|Ruby|2014/8/2(当日)|https://qiita.com/cielavenir/items/9f15e29b73ecf98968a5|
|C#/Python|2014/8/4|https://qiita.com/cielavenir/items/a1156e6a4f71ddbe5dcb|
| |　|ここから上はdrop_prev_square/drop_prev_cubicをまとめる前の答案|
|Go/C#/Ruby/Python|2014/8/5|https://qiita.com/cielavenir/items/2a685d3080862f2c2c47|
|PHP/JavaScript|2014/9/9|https://qiita.com/cielavenir/items/28d613ac3823afbf8407|
|VB|2014/9/10|https://qiita.com/cielavenir/items/cb7266abd30eadd71c04|
|D|2015/12/21|https://qiita.com/cielavenir/items/47c9e50ee60bef2847ec|
|Perl|2017/3/10|https://qiita.com/cielavenir/items/6dfbff749d833c0fd423|
|Lua|2017/3/13|https://qiita.com/cielavenir/items/c60fe7e8da73487ba062|
|C++20(TS)|2017/3/15|https://qiita.com/cielavenir/items/e1129ca185008f49cbab (MSVC)<br>https://qiita.com/cielavenir/items/1cfa90d73d11bb7dc3d4 (clang)|
|F#|2017/3/17|https://qiita.com/cielavenir/items/a698d6a26824ff53de81|
|Boo/Nemerle|2017/5/13|https://qiita.com/cielavenir/items/e2a783f0fe4b0fe0ed48|
|Perl6|2017/5/15|https://qiita.com/cielavenir/items/656ea17fa96c865c4498|
|Kotlin|2017/5/25|https://qiita.com/cielavenir/items/9c46ce8d9d12e51de285|
|Crystal|2018/5/8|https://qiita.com/cielavenir/items/1815bfa6a860fd1f90db|
|MoonScript|2018/6/16|https://qiita.com/cielavenir/items/8b03cce0386f4537b5ad|
|Julia/Rust|2018/12/20|https://qiita.com/cielavenir/items/3ddf72b06d625da0c4a5|
|Nim|2018/12/26|https://qiita.com/cielavenir/items/5728944867e609fd52a7|
|Tcl|2018/12/31|https://qiita.com/cielavenir/items/76cbd9c2022b48c9a2c9|
|Pascal/Cobra|2019/1/16|https://qiita.com/cielavenir/items/81b81baf8dfc1f877903|
|Icon|2019/1/17|https://qiita.com/cielavenir/items/889622dcc721f5a4da24|
|Swift|2020/5/31|https://qiita.com/cielavenir/items/3b0b84a218e35d538f7f|
|Java/Groovy/Scala|2020/5/31|https://qiita.com/cielavenir/items/7f058203a8fd03b65870|
|V|2020/10/17|https://qiita.com/cielavenir/items/df30a6c101a97a713df5|
|Zig/Zen|2020/10/17|https://qiita.com/cielavenir/items/9cced9e4a94dcd70df0f|
|Pike|2020/11/2|https://qiita.com/cielavenir/items/3a8248f41611302b34fd|
|Vala/Smalltalk|2020/11/29|https://qiita.com/cielavenir/items/085dabe593cd916af5e8|
|Objective-C|2020/11/30|https://qiita.com/cielavenir/items/a1736e38789a3dd5cc5a|
|Ruby(Ractor)|2021/1/2|https://qiita.com/cielavenir/items/f493c6d512b63cc571cc|
|Python(_xxsubinterpreters)|2021/6/29|https://qiita.com/cielavenir/items/f1f581a055db918954f1|
|Falcon/Scheme|2021/9/5|https://qiita.com/cielavenir/items/c13d12cf44f0d17f4a94|
|Clojure/Lisp|2021/9/7|https://qiita.com/cielavenir/items/7458ba076f4e5bc0f196|
|(icbrtの実装に関する)補題|2017/5/11|整数除算であってもn/(x*y)はn/x/yに等しい(ことの証明)<br>https://qiita.com/cielavenir/items/21a6711afd6be8c18c55|

40答案到達(全て無限リスト)です。

## Falcon

Falconの関数はクロージャらしい。

checked using 0.9.6.8.

```falcon
#!/usr/bin/env falcon
// http://nabetani.sakura.ne.jp/hena/ord24eliseq/

function isqrt(n)
	if n<=0: return 0
	if n<4: return 1
	x = 0
	y = n
	while x!=y and x+1!=y
		x = y
		y = int((int(n/y)+y)/2)
	end
	return x
end

function icbrt(n)
	if n<0: return -icbrt(-n)
	if n==0: return 0
	if n<8: return 1
	x = 0
	y = n
	while x!=y and x+1!=y
		x = y
		y = int((int(int(n/y)/y)+y*2)/3)
	end
	return x
end

function generate()
	i = 0
	return {=>
		i += 1
		return i
	}
end

function drop_prev(check, prev)
	a = 0
	b = prev()
	return {=>
		while true
			a = b
			b = prev()
			if not check(b)
				return a
			end
		end
	}
end

function drop_next(check, prev)
	first = true
	a = 0
	b = 0
	return {=>
		while true
			a = b
			b = prev()
			if first or not check(a)
				first = false
				return b
			end
		end
	}
end

function drop_n(check, n, prev)
	i = 0
	return {=>
		while true
			i += 1
			a = prev()
			if not check(i,n)
				return a
			end
		end
	}
end

function is_sq(n): return isqrt(n)**2 == n
function is_cb(n): return icbrt(n)**3 == n
function is_multiple(i,n): return i%n == 0
function is_le(i,n): return i<=n

f = [
	"S" => {prev => drop_next(is_sq,prev)},
	"s" => {prev => drop_prev(is_sq,prev)},
	"C" => {prev => drop_next(is_cb,prev)},
	"c" => {prev => drop_prev(is_cb,prev)},
	"h" => {prev => drop_n(is_le,100,prev)}
]
for i in [2:10]
	f[i.toString()] = {x => {prev => drop_n(is_multiple,x,prev)}}(i)
end

stdin=stdIn()
while true
	s = stdin.grabLine()
	if s==0: exit()
	g = generate()
	for c in s.split("")
		g = f[c](g)
	end

	cnt = 0
	ret = ""
	while cnt<10
		if cnt>0: ret+=","
		ret += g()
		cnt += 1
	end
	> ret
end
```

## Scheme

そんでもって　クロージャといえばSchemeなので手を付けておいた(while/ハッシュテーブル等、他のLisp系言語とは相容れない書き方な気がするがもはやご愛嬌)。

```scheme
#!/usr/bin/env gosh
;http://nabetani.sakura.ne.jp/hena/ord24eliseq/

(define (mydiv x y)
	(truncate (/ x y))
)

(define (isqrt_impl n x y)
	(if (or (= x y) (= (+ x 1) y)) x
		(isqrt_impl n y (mydiv (+ (mydiv n y) y) 2))
	)
)

(define (isqrt n)
	(if (<= n 0) 0
		(if (< n 4) 1
			(isqrt_impl n 0 n)
		)
	)
)

(define (icbrt_impl n x y)
	(if (or (= x y) (= (+ x 1) y)) x
		(icbrt_impl n y (mydiv (+ (mydiv (mydiv n y) y) (* y 2)) 3))
	)
)

(define (icbrt n)
	(if (< n 0) (- 0 (icbrt (- 0 n)))
		(if (= n 0) 0
			(if (< n 8) 1
				(icbrt_impl n 0 n)
			)
		)
	)
)

(define (generate)
	(let ((i 0))
		(lambda ()
			(set! i (+ i 1))
			i
		)
	)
)

(define (drop_prev check prev)
	(let ((a 0) (b (prev)))
		(lambda ()
			(set! a b)
			(set! b (prev))
			(while (check b)
				(set! a b)
				(set! b (prev))
			)
			a
		)
	)
)

(define (drop_next check prev)
	(let ((a 0) (b 0) (first #t))
		(lambda ()
			(set! a b)
			(set! b (prev))
			(while (and (not first) (check a))
				(set! a b)
				(set! b (prev))
			)
			(set! first #f)
			b
		)
	)
)

(define (drop_n check n prev)
	(let ((i 0) (a 0))
		(lambda ()
			(set! i (+ i 1))
			(set! a (prev))
			(while (check i n)
				(set! i (+ i 1))
				(set! a (prev))
			)
			a
		)
	)
)

(define (is_sq n)
	(= (expt (isqrt n) 2) n)
)
(define (is_cb n)
	(= (expt (icbrt n) 3) n)
)
(define (is_multiple i n)
	(= (modulo i n) 0)
)
(define (is_le i n)
	(<= i n)
)

(define f (make-hash-table))
(hash-table-put! f #\S (lambda (prev) (drop_next is_sq prev)))
(hash-table-put! f #\s (lambda (prev) (drop_prev is_sq prev)))
(hash-table-put! f #\C (lambda (prev) (drop_next is_cb prev)))
(hash-table-put! f #\c (lambda (prev) (drop_prev is_cb prev)))
(hash-table-put! f #\h (lambda (prev) (drop_n is_le 100 prev)))
(hash-table-put! f #\2 (lambda (prev) (drop_n is_multiple 2 prev)))
(hash-table-put! f #\3 (lambda (prev) (drop_n is_multiple 3 prev)))
(hash-table-put! f #\4 (lambda (prev) (drop_n is_multiple 4 prev)))
(hash-table-put! f #\5 (lambda (prev) (drop_n is_multiple 5 prev)))
(hash-table-put! f #\6 (lambda (prev) (drop_n is_multiple 6 prev)))
(hash-table-put! f #\7 (lambda (prev) (drop_n is_multiple 7 prev)))
(hash-table-put! f #\8 (lambda (prev) (drop_n is_multiple 8 prev)))
(hash-table-put! f #\9 (lambda (prev) (drop_n is_multiple 9 prev)))

(define s (read-line))
(while (not (eof-object? s))
	(define g (fold (lambda (e g) ((hash-table-get f e) g)) (generate) (string->list s)))
	(define i 0)
	(while (< i 10)
		(if (> i 0) (display ","))
		(display (g))
		(set! i (+ i 1))
	)
	(print)
	(set! s (read-line))
)
```