## [squeak-dev] The Trunk: Graphics-mt.404.mcz

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Wed Dec 5 21:31:34 UTC 2018

```Le mer. 5 déc. 2018 à 16:59, Tm Jhnsn <digit at sonic.net> a écrit :

>
> On Dec 4, 2018, at 12:12 AM, marcel.taeumel wrote:
>
> > Yet, such an infix notation for rectangle creation would not be
> > much of an
> > improvement over Rectangle class >> center:extent:.
> >
> > Very interesting. :-) Thoughts?
>
> Balloons inflate, and Smalltalk is quite associated with balloons... :)
>
> Tim J
>

But in this case, should deflate return the center ? (100 at 100 inflate: 50 at 30)
deflate.
I like spread because there is a kind of isotropic notion, we extend in all
directions...

The lexical field of symmetry may fit: we construct a rectangle by taking
those two vertices:
- image of aPoint by symmetry around myself,
- and aPoint.
So it's somehow a mirroring action:

centerPoint mirror: cornerPoint.
centerPoint reflect: cornerPoint.

We could also think of pivoting or unfolding in the 3rd dimension...
But I find the intention very hard to grasp... It's not obvious that the
message should answer a Rectangle rather than a Point.
And the meaning of argument slipped from extent to corner which is a
different action...

I note that inflate, spread, etc... are verbs, while corner: and extent:
are nouns...
We understand corner: and extent: because we may think of them as
attributes of a Rectangle... (or just because we're used to them?)
In this case, diagonal: may fit too, but the difference with extent: is
thin, and I don't find the notion of isotropic spread in it.
In fact, diagonal: might be to vertex:vertex: what corner: is to
origin:corner: because we can define a rectangle by any of its diagonals...

Geometrically, we may also see self and extentPoint as defining the
diagonal by a center and a diameter of circumscribing circle...
So its a kind of circumExtent: that we pass to the center... Not very clear
that it will answer a Rectangle...
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