批处理脚本实现C语言趣味编程百例003：绘制圆

@echo off&setlocal enabledelayedexpansion
for /l %%a in (1,1,20) do (
  for /l %%b in (1,1,20) do (
    set /a a=10-%%a,b=10-%%b
    for %%c in (a b) do set "%%c=!%%c:-=!"
    set /a a=a*a+b*b
　 rem 牛顿迭代法求平方根
    if !a! neq 0 for /l %%a in (1,1,10) do set /a "r=(a+r/a)/2"
    if !r! equ 10 (
       set /p=*<nul
       ) else (
       set /p=  <nul
    )
  )
  echo,
)
pause>nul
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@echo off&setlocal enabledelayedexpansion
echo,&echo,
for /l %%a in (0,1,20) do (
  set /p=          <nul
  for /l %%b in (0,1,20) do (
    set /a a=10-%%a,b=10-%%b
    for %%c in (a b) do set "%%c=!%%c:-=!"
    set /a a=a*a+b*b,r=a-100
    set "r=!r:-=!"
    if !r! leq 5 (
       set /p=* <nul
       ) else (
       set /p=  <nul
    )
  )
  echo,
)
pause>nul
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@echo off&setlocal enabledelayedexpansion
mode con lines=35&echo,&echo,
for /l %%a in (0,1,30) do (
  set /p=          <nul
  for /l %%b in (0,1,30) do (
    set /a a=15-%%a,b=15-%%b&set "flag="
    for %%c in (a b) do set "%%c=!%%c:-=!"
    set /a a=a*a+b*b
    if !a! gtr 92 if !a! lss 204 set "flag=a"
    if !a! gtr 31 if !a! lss 69 set "flag=a"
    if !a! gtr 6 if !a! lss 19 set "flag=a"
    if defined flag (
      set /p=  <nul
      ) else (
      set /p=* <nul
    )
  )
  echo,
)
pause>nul
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@echo off & setlocal enabledelayedexpansion
set /a sz=28, wid=2*sz+1, Cols=2*wid, iMax=wid*wid
for /l %%i in (1 1 !iMax!) do set "scr=　!scr!"
color 0a & mode con cols=!Cols! lines=!wid!
set /a xC=25, yC=30, r=15 & rem 指定圆心及半径
for /l %%n in (1 1 5) do (
  call :mpc
  set /a "xC=!random!%%wid, yC=!random!%%wid, r=!random!%%(wid*2/3-10)+10"
)
echo !scr!& pause & exit /b

:mpc rem midpoint circle algorithm 中点画圆算法
set /a x=0, y=r, d=-r
for /l %%i in (1 1 999) do (
  for %%# in (1 2) do (
    for %%x in (-!x! !x!) do for %%y in (-!y! !y!) do (
      set /a xd=%%x+xC, yd=%%y+yC, "inScr=(xd-1^xd-wid)&(yd-1^yd-wid)
      if !inScr! lss 0 (
        set /a ind=xd+yd*wid+1, lenL=ind-1, lenR=iMax-ind
        for /f "tokens=1,2,3" %%a in ("!lenL! !ind! !lenR!") do (set scr=!scr:~0,%%a!·!scr:~%%b,%%c!)
      )
    )
    set tmp=!x!&set x=!y!& set y=!tmp!
  )
  set /a x+=1, d+=1+(x"<<1)
  if !d! geq 0 set /a y-=1, d-=y"<<1
  if !y! lss !x! exit /b
)
exit /b
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