Feature request: angle aliases

[MarcinCiura]

Take a look at Proposition II.10: https://mathcs.clarku.edu/~djoyce/java/elements/bookII/propII10.html
Joyce's Euclid refers to angle {G} twice as {EGF} and twice as {DGB}, whatever suits the explanation better. It would be great if one could define the angle once and then use it by naming its vertex and any two points on its sides.

[jemmybutton]

Great idea. Done bc7944a
Seems to work, but needs testing.

[MarcinCiura]

In II.10, I can \drawAngle{DGB} and \drawAngle{BGD} (as defined) but \drawAngle{EGF} fails with

>> "Can't construct angle: "
>> angleName
! Not implemented: (string)&(unknown numeric).
...

Am I doing it wrong?

[jemmybutton]

@mciura
BGD is the angle you define and DGB is its alias created with generateAngleSynonyms. But when you reference an angle using arbitrary points, direction matters, otherwise the results may be ambiguous or you won't be able to reference angles greater than 180 degrees. For some reason, i chose CCW direction, so EGF angle won't work (there's no such angle), but FGE would.
There is a bug in this error message though.
Maybe i should have enhanced generateAngleSynonyms algorithm instead, but that would make constructing compound angles more difficult.

[MarcinCiura]

I see, thanks.
FWIW, Euclid's angles are usually considered not to be greater than 180 degrees: https://mathcs.clarku.edu/~djoyce/java/elements/bookI/defI9.html
Just a random thought: maybe it would be possible to try both directions and prefer the CCW one only if both angles exist?

[jemmybutton]

Euclid's angles are usually considered not to be greater than 180 degrees

But it would be nice to leave this possibility open for other uses (from this point of view the fact that you can't define angles greater than 180 degrees is also a problem, though).

Just a random thought: maybe it would be possible to try both directions and prefer the CCW one only if both angles exist?

Thank you, i'll try to do it.