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Subject: Re: [boost] A design for geometric objects
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2008-11-15 21:06:00

Steven Watanabe wrote:

> Wait. How does that work:
> Right triangle models Triangle.
> Equilateral triangle models Triangle.
> Therefore, right triangle can be converted to equilateral triangle?

Actually I meant only the concept it directly models, not the ones which
are indirectly so.
A model of Right triangle can be constructed from any model of Right
triangle, but not from a model of Triangle.

The idea is to be able to have similar mechanisms to that of
containers/ranges with adaptors, such as this example:

SomeContainer a = transform(some_range, some_function);
(actually you have to write
SomeContainer a(
     begin(transform(some_range, some_function)),
     end(transform(some_range, some_function))

with transform = make_transform_range from Boost.RangeEx.

This results in something fairly equivalent to

SomeContainer a;
     some_range.begin(), some_range.end(),

Maybe it shouldn't be required however. For ranges which are proxies or
adaptors it makes little sense to be able to be constructed from any range.

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