Subject: Re: [boost] [fixed_point] Request for interest in a binary fixed point library
From: Christopher Kormanyos (e_float_at_[hidden])
Date: 2012-04-11 16:33:00
> There are difficult decisions to make about the result types of arithmetic operations, analogous to this:
> int32_t a, b;
> int64_t c;
> c = a+b; // oops.
> It is tempting to make the return type of e.g. operator+ large enough
> to accommodate the largest possible sum, and to truncate only when
> the assignment occurs.
Well, everyone dies, as mentioned below, roll-their-own fixed-point.
There will be lots of valid opinions on this one. But I have had good
results from the following policy:
1) Forbid binary arithmetic among fixed-points with non-like parameter types.
2) Support copy construction and copy assignment of differing types, whereby
*this and the LHS of copy-assign, respectively, determine the digits in
the result --- be it larger or smaller (compile-time enable_if is handy here).
> It is perhaps because of this that everyone tends to "roll their own",
> and no standard implementation has emerged.
Which, quite frankly, I have done one time too many.
I definitely crave fixed-point support.
Good luck on the project.
Best regards, Chris.