批处理如何更准确地计算e的值？

chineseman2

1. setlocal delayexpansion
   
2. set a=1
   
3. set b=1
   
4. set c=10000000
   
5. @echo off
   
6. @cls
   
7. :loop
   
8. set /a c=c+(10000000/b)
   
9. set /a a=a+1
   
10. set /a b=b*a
    
11. if %a% equ 500 goto :ex
    
12. goto :loop
    
13. :ex
    
14. set /a c=c-20000000
    
15. @echo E is 2.%c%
    
16. @echo off
    
17. @pause>nul
    

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e本来等于2.718281828...
但是它只给出e=2.7182814和一大堆Divide by zero error.
如何更准确地计算e？（bat计算...)

chineseman2

http://zh.wikipedia.org/wiki/E_(%E6%95%B0%E5%AD%A6%E5%B8%B8%E6%95%B0)

batman

批无法直接计算浮点同时cmd只能计算2^31内的值(-2147483648-2147483647)，用VBS计算循环到171次也就是b=171!时溢出：

1. 
   
2. Dim a, b, c
   
3. b = 1 : c = 10000000
   
4. For i = 1 To 500
   
5.   On Error Resume Next
   
6.   a = a + 1
   
7.   b = b * a
   
8.   c = c + 10000000 / b
   
9.   If Num = "" And Err.Number <> 0 Then Num = i
   
10.   Err.Clear
    
11. Next
    
12. c = c - 20000000
    
13. WScript.Echo "E=2." & c & vbCrLf & Num
    

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terse

再简化一行
一处笔误  貌似没变化

1. 
   
2. @echo off&setlocal enabledelayedexpansion
   
3. set lp=100
   
4. set /a A=10000,M=1000
   
5. set/aLp=(Lp+3)/4*14
   
6. for /l %%i in (%LP% -1 1) do set/a "S+=M*A,R_%%i=S%%%%i,S/=%%i"
   
7.    set /a "E=S/A+M,M=S%%A,Lp-=14"
   
8.    set _E=%_E%%E:~,4%
   
9.    for /l %%i in (!Lp! -14 1) do (
   
10.        for /l %%j in (%%i -1 1) do set/a "S+=R_%%j*A,R_%%j=S%%%%j,S/=%%j"
    
11.        set /a "E=S/A+M,M=S%%A+A"
    
12.        set _E=!_E!!E:~-4!
    
13.    )
    
14. )
    
15. echo;!_E!
    
16. pause

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