Geometry Boost List: Re: [geometry] Concept for CalculationType

Subject: Re: [geometry] Concept for CalculationType
From: Barend Gehrels (barend_at_[hidden])
Date: 2014-05-27 15:55:55

Hi Andrew,

Andrew Hundt wrote On 27-5-2014 21:42:
> I'm trying to learn how to implement simple algorithms generically.
>
> Is there a concept for CalculationType? It is used in 
> matrix_transformers.hpp, but I couldn't find a concept definition.

There is indeed no concept defined, maybe we should do that indeed.

CalculationType should be a numeric type. Can be a type provided by 
default (float,double,long double, or it can sometimes be an integer 
type) or a high precision type (gmp,ttmath). We should add that not all 
algorithms are yet tested with these types - most are tested by ttmath, 
but not on the Regression Matrix (and on my personal system it is a 
while ago).

>
> I'm trying to create a 2d rotate_translate_transformer which rotates a 
> geometry in place then translates it to a specified location, so I'm 
> trying to modify the implementations in matrix_transformers.hpp.
>
> I'm considering having it take a point and an angle rather than 
> x,y,angle. For comparison, the translate_transformer takes an x and y. 
> Does this seem advisable?

I see - this is a bit arbitrary. A point (x,y) is usually a point, while 
translate is over a vector, therefore x(-diff),y(-diff). But indeed, of 
course, it can also be represented as a point.

>
> Would it be best to make the point a separate template parameter from 
> CalculationType?
>
> If I didn't use a point, should there be one CalculationType template 
> parameter for x,y,angle, or should x,y be one type and angle an 
> additional type?

Usually the angle is of a different type than x,y. Because angle is in 
radians, always a FP type, and x,y might be (but not necessarily) an 
integer type. So if it is a general implemenation, and apparently it is, 
I would advice that.

Regards, Barend