Increment Large Double - C# / C Sharp

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I have a string representing a very large number that I need to increment by 1.
Ocurs that when I try to Convert.ToDoubl e("123456789012 345678901234567 890"),
the string representation of my double gives: 1.2345678901234 567E+29. But I
need to full representation, without the exponent.

Does anybody can help me ?
Thanks.

Feb 10 '07 #1

Subscribe Reply

3354

David Browne

"Cris" <Cr**@discussio ns.microsoft.co mwrote in message
news:21******** *************** ***********@mic rosoft.com...

>I have a string representing a very large number that I need to increment
by 1.
Ocurs that when I try to
Convert.ToDoubl e("123456789012 345678901234567 890"),
the string representation of my double gives: 1.2345678901234 567E+29. But
I
need to full representation, without the exponent.

A double precision floating point number does not have sufficient precision
to store that number down to the last 1. You can use a System.Decimal for
numbers up to 79,228,162,514, 264,337,593,543 ,950,335. For full-precision
arithmetic on larger numbers, you will need to break them down yourself (and
do the carries), or use an arbitrary-precision arithmetic library.

David

Feb 10 '07 #2

Jon Skeet [C# MVP]

Cris <Cr**@discussio ns.microsoft.co mwrote:

I have a string representing a very large number that I need to increment by 1.
Ocurs that when I try to Convert.ToDoubl e("123456789012 345678901234567 890"),
the string representation of my double gives: 1.2345678901234 567E+29. But I
need to full representation, without the exponent.

Does anybody can help me ?

Well, I have a DoubleConverter class which will show you the exact
number - but it'll show you that your original number is almost
certainly not stored as you expect it anyway.

See http://www.pobox.com/~skeet/csharp/floatingpoint.html for more
information and a link to DoubleConverter .

If you're okay with "just" 29 digits, the decimal type should be good
enough.

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

Feb 10 '07 #3

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