Re: new approximately equal operators

From: Eyal Rozenberg <eyalroz_at_[hidden]>
Date: Tue, 9 Jun 2020 02:04:11 +0300
What problem would adding this behavior solve? What is its significant
benefit?

If it's merely the desire to write

if (a ~= b)

if (almost_equal(a, b))

or

if (almost_equal<epsilon>(a, b))

(with almost_equal being a utility function you've implemented), then I
doubt the standard committee would find it worthwhile.

On 08/06/2020 22:52, Vishal Oza via Std-Proposals wrote:
> I was wondering if there is any interest in adding approximately equal
> to operators into the language. The main purpose is to compare floating
> point calculations with rounding error, however they could be used for
> similarity of objects or fixed point rounded values as well.
>
> the operator I propose are: ~=, ~< , ~>, ~!
> these operators would translate at least to floating point as
> a ~= b ==> abs(a-b) < epsilon
> a ~< b ==> (a < b) || (abs(a-b) < epsilon)
> a ~> b ==> (a > b) || (abs(a-b) < epsilon)
> a ~! b ==> abs(a-b) >= epsilon
> There are two routes I can see with default implementation this language
> feature. either adding a default epsilon into the language that can be
> set as a global variable or adding some way of tracking errors. I would
> like more feedback on either way of default implementation.
>
> I would also like a way to specify the epsilon value or function for a
> single comparison. the best I can think of is
> a ~=b(c) ==> abs(a-b) < c
> a ~=b:c ==> abs(a-b) < c
> [c]a ~=b ==> abs(a-b) < c
>
> The precedence should be on the same level of all of the current
> comparison operators.
>
> This could be introduced in C++ 23 or later in there is any interate.
>
> Sincerely,
> Vishal Oza
>
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