setBounds is incorrect -- throws away bounds of subsequent diagrams too

[fryguybob]

(Imported from http://code.google.com/p/diagrams/issues/detail?id=34. Original issue from byor...@gmail.com on June 10, 2011, 05:18:21 AM UTC)

For example, consider

(circle 2 |||
square 1.5 # rotateBy (1/8) # withBounds (square 1 :: Diagram Cairo R2))

which should display a circle next to a slightly overlapping diamond. Instead the output is mostly blank (with a hint of a line on the left).

The problem is that a Forgetful monoid is not the right way to override u annotations traveling up the diagram tree (such as bounds). A Forgetful value ends up annihilating not only u values from below it in the tree, but also any from subtrees to the right.

Perhaps the solution is to allow applying extra u annotations both on the left and the right, then making a special monoid (like Forgetful) that can annihilate a "bracketed" section. A ForgetR value kills values to its right, and ForgetL kills to its left, and when they meet they turn into the identity.

[fryguybob]

(Imported. Original comment by byor...@gmail.com on June 10, 2011, 06:10:56 PM UTC)

Fri Jun 10 14:07:27 EDT 2011 Brent Yorgey byorgey@cis.upenn.edu

• add Deletable monoid transformer

Fri Jun 10 14:07:52 EDT 2011 Brent Yorgey byorgey@cis.upenn.edu

• fix for Issue make SubMaps deletable, and add a new function 'localize' for hiding/deleting names #34 (incorrect behavior of setBounds)
  • replace 'applyU' with two functions 'applyUpre' and 'applyUpost' for applying new u
    values both before and after the given subtree
  • replace 'Forgetful (Bounds v)' with 'Deletable (Bounds v)' and implement setBounds
    by making use of applyUpre forgetL . applyUpost forgetR to get rid of only the
    bounds from the current subtree (and not also bounds from any subtrees to the right,
    like Forgetful did).