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dim函數(shù)第三個(gè)參數(shù)設(shè)置截取字符的長度問題

更新時(shí)間：2012年12月10日 17:34:24 作者：

dim函數(shù)的第三個(gè)參數(shù)，也就是截取字符的長度，我在設(shè)置這個(gè)的時(shí)候，出了些問題,提示無效的過程調(diào)用或參數(shù),本文詳細(xì)介紹如何解決

dim函數(shù)的第三個(gè)參數(shù)，也就是截取字符的長度，我在設(shè)置這個(gè)的時(shí)候，出了些問題:response.write mid(up_address,a(i),a(i+1)-1) & “<br />”像我上面這樣寫的時(shí)候，它就會(huì)報(bào)錯(cuò)，提示無效的過程調(diào)用或參數(shù),
response.write mid(up_address,a(i),a(i+1)+1) & “<br />”但是當(dāng)我把其中的a(i+1)-1改為a(i+1)+1時(shí)，就能執(zhí)行了,a(i+1)對(duì)應(yīng)的值是11，可為什么只能減不能加呢?全部代碼如下:
VB code:

復(fù)制代碼代碼如下:

 
dim a(),up_address 
up_address = "aaa djaldk adflj adafadfasdfa afd ad" 
redim a(len(up_address)) 
a(0) = instr(up_address," ") 
response.write a(0) & "<br />" 
if a(0)<>0 then 
for i=0 to len(up_address)-1 
a(i+1) = instr(a(i)+1,up_address," ") 
response.write mid(up_address,a(i),a(i+1)-1) & "<br />" 
if a(i+1)=0 then 
exit for 
end if 
response.write a(i+1) & "<br />" 
next 

end if如上代碼，我是想把字符串按空格分解出來，但是mid的第三個(gè)參數(shù)那出了點(diǎn)問題，我本來是想這樣截取的：
VB code：

復(fù)制代碼代碼如下:

 
mid(up_address,a(i),a(i+1)-a(i)-1) 
‘a(chǎn)(i)是空格的位置 
‘a(chǎn)(i+1)是下一個(gè)空格的位置 
‘a(chǎn)(i+1)-a(i)-1是兩個(gè)空格直間的字符長度 

現(xiàn)在的問題是，經(jīng)測(cè)試，mid的第三個(gè)參數(shù)那，無法使用減法，也就是說，我可以寫a(i+1)+，但不能寫a(i+1)-，想了好久，我一直不明白問題出在哪？應(yīng)該怎么來解決呢？
出現(xiàn)這個(gè)問題是因?yàn)樯厦娴腗ID函數(shù)的第三個(gè)參數(shù)出現(xiàn)了負(fù)數(shù),下面是在網(wǎng)上找的測(cè)試的VBS代碼，原理一樣，如下的代碼：
VBScript code:

復(fù)制代碼代碼如下:

 
dim a(),up_address 
up_address = "aaa djaldk adflj adafadfasdfa afd ad" 
MsgBox len(up_address) '36 
redim a(len(up_address)) 'a(36) 
a(0) = instr(up_address," ") 
MsgBox a(0) 'a(0)=4 
MsgBox a(0) & "<br />" 
if a(0)<>0 then 
for i=0 to len(up_address)-1 
a(i+1) = instr(a(i)+1,up_address," ") 
MsgBox a(i) &" "& (a(i+1)-1)‘這里的結(jié)果為34，-1，所以導(dǎo)致出錯(cuò) 
MsgBox mid(up_address,a(i),a(i+1)-1) & "<br />" 
if a(i+1)=0 then 
exit for 
end if 
MsgBox a(i+1) & "<br />" 
next 
end if 