error in aspfaq #2304??

[Mike]

This is referring to aspfaq #2304...

I've got a column of data that sometimes is null, sometimes is 0, and
sometimes is some other number. I'm filling out a table with it and I
don't want the 0's to show, so I wrote this function to get rid of
them. I looked on aspfaq.com why my simple replace(column, "0", "")
didn't work, and sure enough I found an answer :) However, when I
tried the recommendation it didn't work...

If I do this (basically 2304):

function ReplaceZeros(column)
if len(column) = 0 then
column = ""
else
column = replace(column, "0", "")
end if
ReplaceZeros = column
end function

I get this:

Microsoft VBScript runtime (0x800A005E)
Invalid use of Null: 'Replace'
/tradelist_3.asp, line 100

If I change the code to this it works fine:

function ReplaceZeros(column)
if isNull(column) then
column = ""
else
column = replace(column, "0", "")
end if
ReplaceZeros = column
end function

-Mike

[Bob]

Mike wrote: 

The length of Null (which really means "unknown") will always evaluate to
Null ("unknown"). You cannot know the length of an unknown piece of data.
Since it evaluates to Null, and Null is not equal to 0, this logic fails.
You could reverse the logic of this to:

If len(column) > 0 then
column = replace(column, "0", "")
else
column = ""
end if

or use IsNull as you did. The only problem with using IsNull is if you need
to react to both a Null value and an empty string. Using IsNull would
require this:

If IsNull(somevariable) then
...
elseif somevariable = "" then
... 'this may be the same code as above
else
...
end if

Using "if len(somevariable)> 0 then" results in more concise code.

Bob Barrows


Bob Barrows


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[Aaron]

> if len(column) = 0 then

I had the logic reversed in the article. (Though I believe it worked in
some previous version of VBScript, because I test all code samples before I
post them.)

To illustrate why you can use len>0 to determine not null, but you can't use
len=0 to determine null,

<%
w = "foo"
x = NULL
y = ""
' no z

response.write "Len(w): " & len(w) & "<br>"
response.write "Len(x): " & len(x) & "<br>"
response.write "Len(y): " & len(y) & "<br>"
response.write "Len(z): " & len(z) & "<p>"

lenwg0 = false: lenxg0 = false: lenyg0 = false: lenzg0 = false

if len(w) > 0 then lenwg0 = true
if len(x) > 0 then lenxg0 = true
if len(y) > 0 then lenyg0 = true
if len(z) > 0 then lenzg0 = true

response.write "Len(w) > 0: " & lenwg0 & "<br>"
response.write "Len(x) > 0: " & lenxg0 & "<br>"
response.write "Len(y) > 0: " & lenyg0 & "<br>"
response.write "Len(z) > 0: " & lenzg0 & "<br>"
%>

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