多段階選抜 (Nim)


|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|

```nim:tyama_hena24_enum.nim
#[
/usr/bin/env nim c --nimcache:$HOME/.nimcache --opt:speed --run $0 $@;exit
#]#
proc isqrt(n:int):int =
 if n<=0: return 0
 if n<4: return 1
 var x=0
 var y=n
 while x!=y and x+1!=y:
  x=y
  y=(n div y+y) div 2
 return x

proc icbrt(n:int):int =
 if n<0: return -icbrt(-n)
 if n==0: return 0
 if n<8: return 1
 var x=0
 var y=n
 while x!=y and x+1!=y:
  x=y
  y=(n div y div y+y*2) div 3
 return x

proc generate():iterator:int =
 return iterator:int =
  var i=1
  while true:
   yield i
   i+=1

proc drop_prev(check:proc(x:int):bool,prev:iterator:int):iterator:int =
 return iterator:int =
  var a=prev()
  var b=prev()
  while true:
   if not check(b): yield a
   a=b
   b=prev()

proc drop_next(check:proc(x:int):bool,prev:iterator:int):iterator:int =
 return iterator:int =
  var a=prev()
  var b=prev()
  yield a
  while true:
   if not check(a): yield b
   a=b
   b=prev()

proc drop_n(check:proc(x:int,y:int):bool,n:int,prev:iterator:int):iterator:int =
 return iterator:int =
  var i=0
  while true:
   i+=1
   var a=prev()
   if not check(i,n): yield a

proc is_sq(n:int):bool =
 var x=isqrt(n)
 return x*x==n

proc is_cb(n:int):bool =
 var x=icbrt(n)
 return x*x*x==n

proc is_multiple(i:int,n:int):bool = i mod n==0
proc is_le(i:int,n:int):bool = i<=n

import tables
var f={
 'S':proc(e:iterator:int):iterator:int = drop_next(is_sq,e),
 's':proc(e:iterator:int):iterator:int = drop_prev(is_sq,e),
 'C':proc(e:iterator:int):iterator:int = drop_next(is_cb,e),
 'c':proc(e:iterator:int):iterator:int = drop_prev(is_cb,e),
 'h':proc(e:iterator:int):iterator:int = drop_n(is_le,100,e),
 '2':proc(e:iterator:int):iterator:int = drop_n(is_multiple,2,e),
 '3':proc(e:iterator:int):iterator:int = drop_n(is_multiple,3,e),
 '4':proc(e:iterator:int):iterator:int = drop_n(is_multiple,4,e),
 '5':proc(e:iterator:int):iterator:int = drop_n(is_multiple,5,e),
 '6':proc(e:iterator:int):iterator:int = drop_n(is_multiple,6,e),
 '7':proc(e:iterator:int):iterator:int = drop_n(is_multiple,7,e),
 '8':proc(e:iterator:int):iterator:int = drop_n(is_multiple,8,e),
 '9':proc(e:iterator:int):iterator:int = drop_n(is_multiple,9,e),
}.toTable()
## var handling is strict like Rust ##

import strutils
var s=""
while readLine(stdin,s):
 var z=generate()
 for c in s.strip():
  z=f[c](z)
 for i in 0..9:
  if i>0: write(stdout,',')
  write(stdout,z())
 writeLine(stdout,"")
 flushFile(stdout)
```