(a + 1) «í ¤j©ó a ???

sjgau

¦b ¼Æ¾Ç¤W

(a + 1) «í ¤j©ó a ,
¦ý¬O¡A¥ô¦ó ¹q¸£»y¨¥¡A¥]¨í VBA

¥H¤Uªº µ{¦¡³]­p¤ù¬q

double a, b, c;

a= 1.23;
b= a + 1;

while (b > a) do begin
   a= a*1.001;
   b= a + 1;

end;
// b <= a, ???
print a, b

// why????

sunnyso

¦^´_ 1# sjgau


    :o  ·Qª¾¹D爲¤°»ò. ½Ð¸Ñ»¡.

sunnyso

¦^´_ 2# sunnyso

½Ð½ç±Ð. ¬°¤°»ò©O? «Ü·Qª¾¹D.

sjgau

1. Sub test1052()
   
2.    Dim a As Single, b As Single
   
3.    a = 1.23
   
4.    b = a + 1
   
5.    ' b > a
   
6.    
   
7.    While (b > a)
   
8.       a = a * 1.001
   
9.       b = a + 1
   
10.       
    
11.    Wend
    
12.    ' b < a, why???
    
13.    
    
14.    Cells(3, 1) = a
    
15.    Cells(4, 1) = b
    
16.    ' a= b= 16781740, why???
    
17.    
    
18. 
    
19.    MsgBox ("Done!")
    
20.    
    
21.    
    
22.    
    
23. 
    
24. End Sub

½Æ»s¥N½X

sjgau

¦^´_ 3# sunnyso

¦]¬°¡Asingle ªººÖÂI¼Æ¬O ¥|­Óbyte, 32­Óbits,
¨Ï¥Î 23­Ó bits ªí¥Ü ¼Æ¦rªººë½T«×¡A

2^23 --> no
§â 0.5 ¨ì 1.0 ¤Á³Î¦¨¬° no µ¥¤À¡A
©Ò¥H¡Aºë½T«×´N¬O 1/no

sjgau

Sub test1052()
   Dim a As Double, b As Double
   a = 1.23
   b = a + 1
   ' b > a
   
   While (b > a)
      a = a * 1.001
      b = a + 1
   Wend
   ' b < a, why???
   
   Cells(3, 1) = a
   Cells(4, 1) = b
   ' a= b= 9.01577E+15, why???
   

   MsgBox ("Done!")
End Sub

sjgau

¦pªG¬O ¡Adouble ªººÖÂI¼Æ¬O ¤K­Óbyte, 64­Óbits,
¨Ï¥Î 52­Ó bits ªí¥Ü ¼Æ¦rªººë½T«×¡A

2^53 --> no
§â 0.5 ¨ì 1.0 ¤Á³Î¦¨¬° no µ¥¤À¡A
©Ò¥H¡Aºë½T«×´N¬O 1/no

stillfish00

¦^´_ 3# sunnyso
§A¥i¥H¥ý·Q·Q Single ¥u¦³32¦ì¤¸¬°¦ó³Ì¤j¥iªí¥Ü¨ì 3.402823E38¡C
¥i°Ñ¦Ò IEEE 754  http://zh.wikipedia.org/wiki/IEEE_754

sunnyso

·PÁ¤T¦ì¤j¤j¼ö¤ß¸Ñ»¡. «Ü¨ü±Ð

sjgau

¦^´_ 9# sunnyso


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