IsNumeric Function

What is prefered way to check whether a is a numeric value
Is ther something like IsNumeric function in VB6

Thanks
Mark.

VJ
Sun Apr 18 11:16:36 CDT 2004

The same IsNumeric is available in VB.NET, but the recomendation is to use
the RegEx functions.. here is a sample..

Imports System.Text.RegularExpressions

blnValidData = Regex.IsMatch(Text1.Text, "^\d+$") 'Allows integer,and
comma formatted numbers
If Not blnValidData Then
MsgBox("You can enter numbers only in - " & Text1.Name,
MsgBoxStyle.OKOnly + MsgBoxStyle.Exclamation, "Error")
End If

visit www.regexlib.com for more patterns

VJ

"Mark G" <anonymous@discussions.microsoft.com> wrote in message
news:B70D62E6-BB14-4C86-AD9B-87FF6C9CF390@microsoft.com...
> What is prefered way to check whether a is a numeric value.
> Is ther something like IsNumeric function in VB6?
>
> Thanks,
> Mark.

Chris
Sun Apr 18 11:20:49 CDT 2004

Must say, comparing the two, I'd go for the IsNumeric

"VJ" <vijaybalki@yahoo.com> wrote in message
news:OK7HkDWJEHA.208@tk2msftngp13.phx.gbl...
> The same IsNumeric is available in VB.NET, but the recomendation is to use
> the RegEx functions.. here is a sample..
>
> Imports System.Text.RegularExpressions
>
> blnValidData = Regex.IsMatch(Text1.Text, "^\d+$") 'Allows integer,and
> comma formatted numbers
> If Not blnValidData Then
> MsgBox("You can enter numbers only in - " & Text1.Name,
> MsgBoxStyle.OKOnly + MsgBoxStyle.Exclamation, "Error")
> End If
>
> visit www.regexlib.com for more patterns
>
> VJ
>
> "Mark G" <anonymous@discussions.microsoft.com> wrote in message
> news:B70D62E6-BB14-4C86-AD9B-87FF6C9CF390@microsoft.com...
> > What is prefered way to check whether a is a numeric value.
> > Is ther something like IsNumeric function in VB6?
> >
> > Thanks,
> > Mark.
>
>

Scott
Sun Apr 18 15:39:02 CDT 2004

One problem with IsNumeric is (and always has been) that if the value STARTS
out with a number it will be treated as numeric. For example,

123,456.AA

would be considered numeric by IsNumeric.


"Chris Botha" <chris_s_botha@AT_h.o.t.m.a.i.l.com> wrote in message
news:upDpGJWJEHA.556@TK2MSFTNGP10.phx.gbl...
> Must say, comparing the two, I'd go for the IsNumeric
>
> "VJ" <vijaybalki@yahoo.com> wrote in message
> news:OK7HkDWJEHA.208@tk2msftngp13.phx.gbl...
> > The same IsNumeric is available in VB.NET, but the recomendation is to
use
> > the RegEx functions.. here is a sample..
> >
> > Imports System.Text.RegularExpressions
> >
> > blnValidData = Regex.IsMatch(Text1.Text, "^\d+$") 'Allows integer,and
> > comma formatted numbers
> > If Not blnValidData Then
> > MsgBox("You can enter numbers only in - " & Text1.Name,
> > MsgBoxStyle.OKOnly + MsgBoxStyle.Exclamation, "Error")
> > End If
> >
> > visit www.regexlib.com for more patterns
> >
> > VJ
> >
> > "Mark G" <anonymous@discussions.microsoft.com> wrote in message
> > news:B70D62E6-BB14-4C86-AD9B-87FF6C9CF390@microsoft.com...
> > > What is prefered way to check whether a is a numeric value.
> > > Is ther something like IsNumeric function in VB6?
> > >
> > > Thanks,
> > > Mark.
> >
> >
>
>

Chris
Sun Apr 18 16:02:19 CDT 2004

Scott, maybe in VB6, but your example will evaluate to false in .NET.
One problem that was and still is, is something like 123E1 , which can mean
numeric 1230 if so intended, or an error if miss-typed.

"Scott M." <s-mar@BADSPAMsnet.net> wrote in message
news:u$ZAUVYJEHA.3120@TK2MSFTNGP11.phx.gbl...
> One problem with IsNumeric is (and always has been) that if the value
STARTS
> out with a number it will be treated as numeric. For example,
>
> 123,456.AA
>
> would be considered numeric by IsNumeric.
>
>
> "Chris Botha" <chris_s_botha@AT_h.o.t.m.a.i.l.com> wrote in message
> news:upDpGJWJEHA.556@TK2MSFTNGP10.phx.gbl...
> > Must say, comparing the two, I'd go for the IsNumeric
> >
> > "VJ" <vijaybalki@yahoo.com> wrote in message
> > news:OK7HkDWJEHA.208@tk2msftngp13.phx.gbl...
> > > The same IsNumeric is available in VB.NET, but the recomendation is to
> use
> > > the RegEx functions.. here is a sample..
> > >
> > > Imports System.Text.RegularExpressions
> > >
> > > blnValidData = Regex.IsMatch(Text1.Text, "^\d+$") 'Allows
integer,and
> > > comma formatted numbers
> > > If Not blnValidData Then
> > > MsgBox("You can enter numbers only in - " & Text1.Name,
> > > MsgBoxStyle.OKOnly + MsgBoxStyle.Exclamation, "Error")
> > > End If
> > >
> > > visit www.regexlib.com for more patterns
> > >
> > > VJ
> > >
> > > "Mark G" <anonymous@discussions.microsoft.com> wrote in message
> > > news:B70D62E6-BB14-4C86-AD9B-87FF6C9CF390@microsoft.com...
> > > > What is prefered way to check whether a is a numeric value.
> > > > Is ther something like IsNumeric function in VB6?
> > > >
> > > > Thanks,
> > > > Mark.
> > >
> > >
> >
> >
>
>

Jon
Tue Apr 20 03:10:22 CDT 2004

VJ <vijaybalki@yahoo.com> wrote:
> The same IsNumeric is available in VB.NET, but the recomendation is to use
> the RegEx functions..

That may be *your* recommendation. It's certainly not mine :)

Rather than using regular expressions, it's very easy to write a method
which quickly knocks out most "obviously" non-numeric strings.

Having done that, you can use Double.TryParse.

This approach is significantly faster than using regular expressions
(in the tests I did a while ago, at least).

--
Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

Alvin
Tue Apr 20 10:35:31 CDT 2004

> This approach is significantly faster than using regular expressions
> (in the tests I did a while ago, at least).
can you point me to those test?

Tryparse actually throws an exception on an invalid format. I'm not sure
that a live exception is faster than a regex compilation and execution. It
would make sense that if the data was significantly faulty, or perhaps
generally unknown that the use of a regex would be a suitable optimization
to avoid the run-time exceptions.

--
Regards,
Alvin Bruney [ASP.NET MVP]
Got tidbits? Get it here...
http://tinyurl.com/27cok
"Jon Skeet [C# MVP]" <skeet@pobox.com> wrote in message
news:MPG.1aeedc8f39401e9298a6db@msnews.microsoft.com...
> VJ <vijaybalki@yahoo.com> wrote:
>> The same IsNumeric is available in VB.NET, but the recomendation is to
>> use
>> the RegEx functions..
>
> That may be *your* recommendation. It's certainly not mine :)
>
> Rather than using regular expressions, it's very easy to write a method
> which quickly knocks out most "obviously" non-numeric strings.
>
> Having done that, you can use Double.TryParse.
>
> This approach is significantly faster than using regular expressions
> (in the tests I did a while ago, at least).
>
> --
> Jon Skeet - <skeet@pobox.com>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too

Jon
Tue Apr 20 12:47:40 CDT 2004

<"Alvin Bruney [MVP]" <vapor at steaming post office>> wrote:
> > This approach is significantly faster than using regular expressions
> > (in the tests I did a while ago, at least).
>
> can you point me to those test?

Sure. Have a look on groups.google.com for "Checking if a string can be
converted to Int32" (in this group).

> Tryparse actually throws an exception on an invalid format. I'm not sure
> that a live exception is faster than a regex compilation and execution.

Um, I don't think TryParse *does* throw an exception - the whole point
is that it doesn't, surely?

> It would make sense that if the data was significantly faulty, or perhaps
> generally unknown that the use of a regex would be a suitable optimization
> to avoid the run-time exceptions.

No it wouldn't - not compared with a simple hard coded test and then
using TryParse.

Here are the results I got from the benchmark in the thread mentioned
earlier:

Benchmarking type StringToInt
JustException: 00:01:15.7989936
HardCodedCheck: 00:00:00.7010080
DoubleTryParse: 00:00:40.8387232
Regex: 00:00:43.0418912
IsNumeric: 00:01:06.9062064

(It does the obvious thing.)

Yes, the hard-coded test is over 50x faster than the next-best, which
is Double.TryParse.

--
Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

mikeb
Tue Apr 20 17:17:31 CDT 2004

Jon:

I've seen you put forth and defend this algorithm several times. I
suggest you add this to your FAQ - maybe in the "Converting to C# from
VB.NET" section. It's not only a FAQ, but it's one that seems to get
you sucked into a lengthy explanation each time.

Jon Skeet [C# MVP] wrote:

> <"Alvin Bruney [MVP]" <vapor at steaming post office>> wrote:
>
>>>This approach is significantly faster than using regular expressions
>>>(in the tests I did a while ago, at least).
>>
>>can you point me to those test?
>
>
> Sure. Have a look on groups.google.com for "Checking if a string can be
> converted to Int32" (in this group).
>
>
>>Tryparse actually throws an exception on an invalid format. I'm not sure
>>that a live exception is faster than a regex compilation and execution.
>
>
> Um, I don't think TryParse *does* throw an exception - the whole point
> is that it doesn't, surely?
>
>
>>It would make sense that if the data was significantly faulty, or perhaps
>>generally unknown that the use of a regex would be a suitable optimization
>>to avoid the run-time exceptions.
>
>
> No it wouldn't - not compared with a simple hard coded test and then
> using TryParse.
>
> Here are the results I got from the benchmark in the thread mentioned
> earlier:
>
> Benchmarking type StringToInt
> JustException: 00:01:15.7989936
> HardCodedCheck: 00:00:00.7010080
> DoubleTryParse: 00:00:40.8387232
> Regex: 00:00:43.0418912
> IsNumeric: 00:01:06.9062064
>
> (It does the obvious thing.)
>
> Yes, the hard-coded test is over 50x faster than the next-best, which
> is Double.TryParse.
>


--
mikeb

Jon
Wed Apr 21 01:53:30 CDT 2004

mikeb <mailbox.google@nospam.mailnull.com> wrote:
> I've seen you put forth and defend this algorithm several times. I
> suggest you add this to your FAQ - maybe in the "Converting to C# from
> VB.NET" section. It's not only a FAQ, but it's one that seems to get
> you sucked into a lengthy explanation each time.

Yes, good idea :)

I'll try to get round to it later today.

--
Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

Alvin
Thu Apr 22 10:21:33 CDT 2004

I don't think i found the exact thread but what i found i used which just
had the hard check and exception.
I also have a monster laptop

No extra checking: 00:00:30.4537904
(Total=65554500000)
With preliminary checking: 00:00:00.2603744
(Total=65554500000)

Your conclusions are correct.

>> Tryparse actually throws an exception on an invalid format. I'm not sure
>> that a live exception is faster than a regex compilation and execution.
i really don't know where i got that from. it's obviously wrong.

Another important point is that running this test under visual studio skews
each result by about 5% - 15% when the debugger is not attached in both
release and debug mode. Attaching the debugger provided results which took
over 10 minutes. I've concluded that timing applications by using visual
studio is unreliable at best since the skew is not a constant value for each
result.

--
Regards,
Alvin Bruney [ASP.NET MVP]
Got tidbits? Get it here...
http://tinyurl.com/27cok
"Jon Skeet [C# MVP]" <skeet@pobox.com> wrote in message
news:MPG.1aef72976181fb9c98a6f8@msnews.microsoft.com...
> <"Alvin Bruney [MVP]" <vapor at steaming post office>> wrote:
>> > This approach is significantly faster than using regular expressions
>> > (in the tests I did a while ago, at least).
>>
>> can you point me to those test?
>
> Sure. Have a look on groups.google.com for "Checking if a string can be
> converted to Int32" (in this group).
>
>> Tryparse actually throws an exception on an invalid format. I'm not sure
>> that a live exception is faster than a regex compilation and execution.
>
> Um, I don't think TryParse *does* throw an exception - the whole point
> is that it doesn't, surely?
>
>> It would make sense that if the data was significantly faulty, or perhaps
>> generally unknown that the use of a regex would be a suitable
>> optimization
>> to avoid the run-time exceptions.
>
> No it wouldn't - not compared with a simple hard coded test and then
> using TryParse.
>
> Here are the results I got from the benchmark in the thread mentioned
> earlier:
>
> Benchmarking type StringToInt
> JustException: 00:01:15.7989936
> HardCodedCheck: 00:00:00.7010080
> DoubleTryParse: 00:00:40.8387232
> Regex: 00:00:43.0418912
> IsNumeric: 00:01:06.9062064
>
> (It does the obvious thing.)
>
> Yes, the hard-coded test is over 50x faster than the next-best, which
> is Double.TryParse.
>
> --
> Jon Skeet - <skeet@pobox.com>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too