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Nov 22nd, 2008

How to generate an uniqe number always?

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Hi ,

can any one tell me how to generate an unique number ?
this can be done in C# with great ease. But i wonder how to generate tat in c++

koushal.vv

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

C++ Syntax (Toggle Plain Text)
int getUnique() {
  static int n = 0;
  return ++n;
}
int getUnique() {
  static int n = 0;
  return ++n;
}

This function is not multithreading safe.

Rashakil Fol

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

>this can be done in C# with great ease
Oh good. Show us how you do it in C# so we know what the hell you're talking about by a "unique number".

Narue

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

C++ Syntax (Toggle Plain Text)
            Console.WriteLine(System.Guid.NewGuid().ToString());
            Console.WriteLine(System.Guid.NewGuid().ToString());

koushal.vv

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

There is no such thing as a truly unique number, especially in computing. The seed is generally the time.

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

http://msdn.microsoft.com/en-us/libr...stem.guid.aspx

Quote ...

A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.

How low of a probability are you looking for?

VernonDozier

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

i am storing some data in the database,
for tat i always need to send a unique value to it,
if the value already exists then an exception will be thrown.
so when ever i am storing in the db the value have to be unique.

koushal.vv

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Nov 22nd, 2008

Re: How to generate an uniqe number always?

Start your "unique number" at 1 and increment it for each new data record. That seems to be the easiest and safest way to make all your numbers unique.

WaltP

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Nov 23rd, 2008

Re: How to generate an uniqe number always?

What if i run the program again, then again it starts with 1,
so i would get a exception

koushal.vv

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Nov 23rd, 2008

Re: How to generate an uniqe number always?

then start at a value 1 more than the highest in the dB, if you wish to use incrementing type indexes. Or you could use the number of microseconds since (e.g.) 12:00am jan 1900 UTC as your 'unique number'.

Last edited by dougy83; Nov 23rd, 2008 at 2:39 am.

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