 # STD-PROPOSALS

Subject: Re: [std-proposals] new approximately equal operators
From: Vishal Oza (vickoza_at_[hidden])
Date: 2020-06-08 17:25:37

for you questions

1. epsilon would be a very small number close to zero but not zero.
Having epsilon as a variable might not be needed in there is a way to track
the accuracy of floating point error over the course of the calculation to
the operator.or we might be about to use the exponent to compute what
epsilon value seem reasonable
2. yes it can be but it is extra pointless work the only reason I use
abs(a-b) is to remove the sign is the number is negative. It might also
this to work with complex number but I this I would have to explore this
further.
3. assignment of ~= does not compile in current C++ but in what I
propose a ~= 5000(0.1) would translate to abs(a-5000) < 0.1

int f = 5000;
float x = 0.1;
auto a == f(x);

int caruso(int a);

auto a == caruzo(f)(x);
or...
auto a == ( caruzo(f) )(x);

On Mon, Jun 8, 2020 at 3:06 PM Nikolay Mihaylov <nmmm_at_[hidden]> wrote:

> 1. What is epsilon?
> 2. didn't this abs(a-b) be abs(abs(a)-abs(b))
> 3. a ~=b(c) - b(c) this actually will be:
>
> auto a ~= 5000(0.1);
>
> int f = 5000;
> float x = 0.1;
> auto a ~= f(x);
>
>
> int caruso(int a);
>
> auto a ~= caruzo(f)(x);
> or...
> auto a ~= ( caruzo(f) )(x);
>
>
>
>
> On Mon, Jun 8, 2020 at 10:55 PM Vishal Oza via Std-Proposals <
> std-proposals_at_[hidden]> 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
>> --
>> Std-Proposals mailing list
>> Std-Proposals_at_[hidden]

>>
>

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