Re: [boost] Large Integer Library

Subject: Re: [boost] Large Integer Library
From: Rafaël Fourquet (fourquet.d+boost_at_[hidden])
Date: 2012-06-30 11:10:53

>
>   Please, if you have the time, download this library and give it a try.
>  Any
> comments, or information upon its compatibility (or lack thereof) with
> compilers which are or are not listed would be greatly appreciated.
>

I started playing with your library using gcc 4.7.1 and it seems
compatible. I will definitely want to use it instead of my own unfinished
and probably buggy implementation. A few questions:

1) Could the programmer be given access (through member functions) to the
two members of a large_int? For example, I need a function to swap the high
and low bits of an integer-like value x. When x is of type large_int<T, T>,
I guess it would be more efficient to manipulate directly the two members
x.m_lo and x.m_hi instead of using the usual bit-operations.

2) The typedef for l[u]int128_t does not seem to use the builtin
corresponding type when available, could this be done?

3) I had "undefined symbol" problems when using the builtin 128 bits
integers (provided by gcc) in the signature of functions in a shared
library (it was a module created with Boost.Python, the problem occurred
when importing this module within python). The only solution I found was to
wrap integer-like types inside a (templated) class, which looks like a
particular case of your library (this would be "large_int<EMPTY_TYPE, U>").
Would LargeInt be an appropriate place to solve this problem?

4) Why use Boost.Operator for some operators but not all (e.g. comparison
operators)?

Thanks,
Rafael