Re: Check to see a string or single character is a number or character??
- From: "Rick Rothstein [MVP - Visual Basic]" <rickNOSPAMnews@xxxxxxxxxxxxxxxxx>
- Date: Fri, 26 Aug 2005 12:58:41 -0400
> Hey, Quite new to VB and I have been searching how to do this with no
> luck. I have a single character and I want to check to see if it is a
> number or a character. Could someone please tell me how to go about
> this? BTW, I am using VB 6.0
If it is ONLY a single character, you can use VB's IsNumeric function;
it will work fine for this situation. However, if your String is more
than one character long, then I would advise against the IsNumeric
function. Why? From a previous post of mine...
I usually try and steer people away from using IsNumeric to "proof"
supposedly numeric text. Consider this (also see note at end of post):
ReturnValue = IsNumeric("($1,23,,3.4,,,5,,E67$)")
Most people would not expect THAT to return True. IsNumeric has some
"flaws" in what it considers a proper number and what most programmers
are looking for.
I had a short tip published by Pinnacle Publishing in their Visual Basic
Developer magazine that covered some of these flaws. Originally, the tip
was free to view but is now viewable only by subscribers.. Basically, it
said that IsNumeric returned True for things like -- currency symbols
being located in front or in back of the number as shown in my example
(also applies to plus, minus and blanks too); numbers surrounded by
parentheses as shown in my example (some people use these to mark
negative numbers); numbers containing any number of commas before a
decimal point as shown in my example; numbers in scientific notation (a
number followed by an upper or lower case "D" or "E", followed by a
number equal to or less than 305 -- the maximum power of 10 in VB); and
Octal/Hexadecimal numbers (&H for Hexadecimal, &O or just & in front of
the number for Octal).
NOTE:
======
In the above example and in the referenced tip, I refer to $ signs and
commas and dots -- these were meant to refer to your currency, thousands
separator and decimal point symbols as defined in your local settings --
substitute your local regional symbols for these if appropriate.
As for your question about checking numbers, here are two functions that
I have posted in the past for similar questions..... one is for digits
only and the other is for "regular" numbers:
Function IsDigitsOnly(Value As String) As Boolean
IsDigitsOnly = Len(Value) > 0 And _
Not Value Like "*[!0-9]*"
End Function
Function IsNumber(ByVal Value As String) As Boolean
' Leave the next statement out if you don't
' want to provide for plus/minus signs
If Value Like "[+-]*" Then Value = Mid$(Value, 2)
IsNumber = Not Value Like "*[!0-9.]*" And _
Not Value Like "*.*.*" And _
Len(Value) > 0 And Value <> "." And _
Value <> vbNullString
End Function
Here are revisions to the above functions that deal with the local
settings for decimal points (and thousand's separators) that are
different than used in the US (this code works in the US too, of
course).
Function IsNumber(ByVal Value As String) As Boolean
Dim DP As String
' Get local setting for decimal point
DP = Format$(0, ".")
' Leave the next statement out if you don't
' want to provide for plus/minus signs
If Value Like "[+-]*" Then Value = Mid$(Value, 2)
IsNumber = Not Value Like "*[!0-9" & DP & "]*" And _
Not Value Like "*" & DP & "*" & DP & "*" And _
Len(Value) > 0 And Value <> DP And _
Value <> vbNullString
End Function
I'm not as concerned by the rejection of entries that include one or
more thousand's separators, but we can handle this if we don't insist on
the thousand's separator being located in the correct positions (in
other words, we'll allow the user to include them for their own
purposes... we'll just tolerate their presence).
Function IsNumber(ByVal Value As String) As Boolean
Dim DP As String
Dim TS As String
' Get local setting for decimal point
DP = Format$(0, ".")
' Get local setting for thousand's separator
' and eliminate them. Remove the next two lines
' if you don't want your users being able to
' type in the thousands separator at all.
TS = Mid$(Format$(1000, "#,###"), 2, 1)
Value = Replace$(Value, TS, "")
' Leave the next statement out if you don't
' want to provide for plus/minus signs
If Value Like "[+-]*" Then Value = Mid$(Value, 2)
IsNumber = Not Value Like "*[!0-9" & DP & "]*" And _
Not Value Like "*" & DP & "*" & DP & "*" And _
Len(Value) > 0 And Value <> DP And _
Value <> vbNullString
End Function
Rick
.
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