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How can I do this without Regex ?


Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9]+$" ))
{
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.

Thanks in advance,

P.S.
Is there in C# something similar to Delphi's sets ?

Nov 15 '05 #1
9 4296
Tim Conner <Ti*******@discussions.microsoft.com> wrote:
Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9]+$" ))
{
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.


While regular expressions are very powerful, they're not very fast for
doing simple thing - and you're creating a new string for each call as
well. Far simpler and faster is:

public static bool IsNumber (char value)
{
return (value>='0' && value <='9');
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Nov 15 '05 #2
Why don't you try the framework given method ?
Check the Char.IsNumber( ) ?

For example :
Console.WriteLine(Char.IsNumber('8')); // Output: "True"

"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP************************@msnews.microsoft.c om...
Tim Conner <Ti*******@discussions.microsoft.com> wrote:
Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9]+$" ))
{
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.


While regular expressions are very powerful, they're not very fast for
doing simple thing - and you're creating a new string for each call as
well. Far simpler and faster is:

public static bool IsNumber (char value)
{
return (value>='0' && value <='9');
}

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

Nov 15 '05 #3
Tim,
In addition to Jon's comments.

Is there a reason you are not using the static Char.IsDigit or Char.IsNumber
function?
public static bool IsNumber( char Value )
{ return Char.IsDigit(Value); }
Char has a number of other static functions that check the character's
class.

FWIW, when I have a static method that is checking a 'constant' regex, I
normally create a static Regex field, then use that. This way the regex
object itself is not continueally recreated. I even consider making this
Regex compiled with the RegexOptions.Compiled option, to get even a little
more performance out of it. Seeing as its static, there is only going to be
one anyway.

Something like:

static readonly Regex thePattern = new Regex(@"^[0-9]+$",
RegexOptions.Compiled);
public static bool IsNumber( string value )
{ return thePattern.IsMatch(value); }
Hope this helps
Jay
"Tim Conner" <Ti*******@discussions.microsoft.com> wrote in message
news:08****************************@phx.gbl...
Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9]+$" ))
{
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.

Thanks in advance,

P.S.
Is there in C# something similar to Delphi's sets ?

Nov 15 '05 #4

I have another similar routines, for check alpha numeric,
and to test for integers and floats. So, I did that just
by inertia <g>. I may change this routine since it is very
straight forward, numbers are numbers, so no more to check
here.

But for my other routines, I think I do need regex. For
example the following :

public static bool IsFloat( string Value)
{
if (Regex.IsMatch( Value.ToString(), @"^[+-]?([0-9]*\.?
[0-9]+|[0-9]+\.?[0-9]*)([eE][+-]?[0-9]+)?$" ))
{
return true;
}
else return false;

}
I am using the static IsMatch of Regex. So I think I am
not recreating a regex object each time.
But your code seems slightly different.
But I am not sure about "that" difference <g>.
Would you mind to explain a bit more on this ?
Thanks in advance,


-----Original Message-----
Tim,
In addition to Jon's comments.

Is there a reason you are not using the static Char.IsDigit or Char.IsNumberfunction?
public static bool IsNumber( char Value )
{ return Char.IsDigit(Value);
}


Char has a number of other static functions that check

the character'sclass.

FWIW, when I have a static method that is checking a 'constant' regex, Inormally create a static Regex field, then use that. This way the regexobject itself is not continueally recreated. I even consider making thisRegex compiled with the RegexOptions.Compiled option, to get even a littlemore performance out of it. Seeing as its static, there is only going to beone anyway.

Something like:

static readonly Regex thePattern = new Regex(@"^[0-9] +$",RegexOptions.Compiled);
public static bool IsNumber( string value )
{ return thePattern.IsMatch(value);
}


Hope this helps
Jay
"Tim Conner" <Ti*******@discussions.microsoft.com> wrote

in messagenews:08****************************@phx.gbl...

Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9] +$" )) {
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.

Thanks in advance,

P.S.
Is there in C# something similar to Delphi's sets ?

.

Nov 15 '05 #5
Tim,
I am using the static IsMatch of Regex. So I think I am
not recreating a regex object each time. Correct you are not explicitly creating a regex object each time, however
the static method IS implicitly creating a regex object each time for you.
Read the description of the static IsMatch carefully!

http://msdn.microsoft.com/library/de...atchTopic3.asp

The Remarks state: "The two static IsMatch methods are equivalent to
constructing a Regex object with the specified regular expression pattern
and calling the instance method IsMatch. The static methods are provided to
allow an isolated, single use of a regular expression without explicitly
creating a Regex object."

Note "isolated, single use" and "equivalent to constructing a regex object"
in the above statement. I would expect your IsFloat method to be called a
number of different times from a number of different places...
But your code seems slightly different.
But I am not sure about "that" difference <g>.
Would you mind to explain a bit more on this ? What do you mean different? Do you mean I simply return the bool value,
rather then checking for true and returning true?

you effectively have:

bool rc = Regex.IsMath(...)

if (rc)
return true
else
return false;

where as I effectively have:

bool rc = Regex.IsMath(...)

return rc;

I used an explaining variable in the above sample, however they are the
same.

Or that you were passing a char, I modified it to pass a string.

Or that I created an object, and use an instance method of the object?

In your IsFloat routine, I would simply use:

private static readonly Regex floatPattern = new
Regex(@"^[+-]?([0-9]*\.?[0-9]+|[0-9]+\.?[0-9]*)([eE][+-]?[0-9]+)?$",
RegexOptions.Compiled);

public static bool IsFloat(string value)
{
return floatPattern.IsMatch(value)
}

floatPattern is:
- private : as its an implementation detail
- static : as we only need one instance of it
- readonly : as we don't need to change it after its initialized

IsFloat uses the above Regex to check for a match, value is already a
string, so we do not need to call ToString a second time. Seeing as
Regex.IsMatch returns a bool, we can simply return this bool. IsFloat
encapsulates the Regex object.

Hope this helps
Jay

"Tim Conner" <Ti*******@discussions.microsoft.com> wrote in message
news:09****************************@phx.gbl...
I have another similar routines, for check alpha numeric,
and to test for integers and floats. So, I did that just
by inertia <g>. I may change this routine since it is very
straight forward, numbers are numbers, so no more to check
here.

But for my other routines, I think I do need regex. For
example the following :

public static bool IsFloat( string Value)
{
if (Regex.IsMatch( Value.ToString(), @"^[+-]?([0-9]*\.?
[0-9]+|[0-9]+\.?[0-9]*)([eE][+-]?[0-9]+)?$" ))
{
return true;
}
else return false;

}
I am using the static IsMatch of Regex. So I think I am
not recreating a regex object each time.
But your code seems slightly different.
But I am not sure about "that" difference <g>.
Would you mind to explain a bit more on this ?
Thanks in advance,


-----Original Message-----
Tim,
In addition to Jon's comments.

Is there a reason you are not using the static

Char.IsDigit or Char.IsNumber
function?
public static bool IsNumber( char Value )
{

return Char.IsDigit(Value);
}


Char has a number of other static functions that check

the character's
class.

FWIW, when I have a static method that is checking

a 'constant' regex, I
normally create a static Regex field, then use that. This

way the regex
object itself is not continueally recreated. I even

consider making this
Regex compiled with the RegexOptions.Compiled option, to

get even a little
more performance out of it. Seeing as its static, there

is only going to be
one anyway.

Something like:

static readonly Regex thePattern = new Regex(@"^[0-9]

+$",
RegexOptions.Compiled);
public static bool IsNumber( string value )
{

return thePattern.IsMatch(value);
}


Hope this helps
Jay
"Tim Conner" <Ti*******@discussions.microsoft.com> wrote

in message
news:08****************************@phx.gbl...

Is there a way to write a faster function ?

public static bool IsNumber( char Value )
{
if (Regex.IsMatch( Value.ToString(), @"^[0-9] +$" )) {
return true;
}
else return false;
}

I think, if I have to repat this some thousands time, it
could become very time consuming.

Thanks in advance,

P.S.
Is there in C# something similar to Delphi's sets ?

.

Nov 15 '05 #6
> I have another similar routines, for check alpha numeric,
and to test for integers and floats. So, I did that just
by inertia <g>. I may change this routine since it is very
straight forward, numbers are numbers, so no more to check
here.

Don't validate to much.
Some day the marketing team will decide they can sell
this in Europe and you have to translate it.
And suddenly you validations go down the drain.
Your alpha numeric will not accept accented characters,
your float will not accept numbers where the
decimal point is comma, etc.

Mihai
Nov 15 '05 #7
Bsiang Tan <tb*********@hotmail.com> wrote:
Why don't you try the framework given method ?
Check the Char.IsNumber( ) ?

For example :
Console.WriteLine(Char.IsNumber('8')); // Output: "True"


Actually, what was asked for is really Char.IsDigit (ie just 0-9) - but
I wouldn't have spotted that if you hadn't raised it :)

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Nov 15 '05 #8
The simplest would be to do a float.Parse(myString) and check wheather a
exception occures or not.

--
cody

[Freeware, Games and Humor]
www.deutronium.de.vu || www.deutronium.tk
Nov 15 '05 #9
codymanix <do*********************@gmx.de> wrote:
The simplest would be to do a float.Parse(myString) and check wheather a
exception occures or not.


And the fastest would be to do some preliminary validation before
calling float.Parse. Again, writing a small routine which knows about
floating point formats is likely to be fairly simple, and significantly
faster than a regex.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Nov 15 '05 #10

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