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NNTP-Posting-Date: Tue, 03 May 2011 16:17:16 -0500
From: Pete Becker <pete@versatilecoding.com>
Organization: Roundhouse Consulting, Ltd.
Newsgroups: comp.lang.c++
Date: Tue, 3 May 2011 17:17:16 -0400
Message-ID: <2011050317171672135-pete@versatilecodingcom>
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Subject: Re: literals for an int128 class
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On 2011-05-03 16:39:35 -0400, cps said:

> I am considering writing an int128 class as a programming exercise.
> Before I start (and I have a fair idea of how to do it) I was
> wondering what I can do about literals and the assignment operator.  I
> would like to be able to use integer literals with the assignment and
> other operators with literals that are sized at 128 bits.
> 
> E.g. I'd like to be able to do:
> 
>      uint128 myInt128 = 184467440737095516160;
> 
> 
>      Note that the foregoing literal would produce an error (correctly
> so) if I attempted to assign it to an uint64 because it is (2^64) *
> 10.
> 
>      Is there any way I can set it up to deal with large literals?
> 
>     Or am I going to have to use strings and parse them?

You can't do 128 bit literals if your compiler doesn't support them, 
but you can do something that's a little easier than parsing a string.

struct uint128 {
	uint128(unsigned long long word1, unsigned long long word0);
};

uint128 i0(0x21, 0x03);
uint128 i1(0x0, 3);



-- 
  Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The 
Standard C++ Library Extensions: a Tutorial and Reference 
(www.petebecker.com/tr1book)