Re: [boost] big integer implementation

From: Jarrad Waterloo (jwaterloo_at_[hidden])
Date: 2006-07-12 14:15:47

It would be nice if there was an api abstraction over the carry flag.
Even better if there was an abstraction over extended add, subtract, divide
and multiply on int and uint arrays. I would however prefer [u]int<size_t>
template that uses the above methods rather than a specific u/int128_t,
u/int192_t, u/int256_t.
These were some of my existing comments on other big integer libraries of a
need of larger fixed sized integer that could be used on the stack. There
still has been no answer.

-----Original Message-----
From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]
On Behalf Of Brannon King
Sent: Wednesday, July 12, 2006 12:03 PM
To: boost_at_[hidden]
Subject: [boost] big integer implementation

So does the big integer class use the CPU's carry flag? I'm picturing an
implementation where you chop the dataset into int32_t. Then, for the add
operation, each piece is composed of a.int32_t[x]+b.int32_t[x]+carry flag of
the previous operation. Does that sound right? If so, I'm wondering how
you're using the carry flag. Do you get that using assembly code or is there
some standard C/C++ command to give you access to that? (Or would somebody
mind taking a second and pointing me to the correct location for the code
for that?)

Using the above method, I think it would be quite useful to have these
dataset types:
u/int128_t, u/int192_t, u/int256_t
Anyone else agree?
 
______________________________
Brannon King
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