more correct emulation of \box and \copy primitives #2480
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| @@ -227,6 +227,23 @@ sub shiftValue { | |||
| assign_internal($self, 'value', $key, [], 'global') unless $$vtable{$key}[0]; | |||
| return shift(@{ $$vtable{$key}[0] }); } | |||
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| sub removeValue { | |||
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You could use this code to implement scope => 'samelevel' assignments (with a better name, if you can find it), which would be equivalent to removeValue when assigning \undef. Should you one day discover another assignment 'in place'.
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That's also a possibility. My main worry is that assign_internal is already somewhat entangled, so adding more to it just makes life harder... Will wait for feedback from Bruce.
I enjoy the idea of having a dedicated removal method, for what that's worth. But since the removal isn't global, the name is a bit misleading. It's really UnbindLastValueAssignment, but this is not a Java project...
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That's also a possibility. My main worry is that
assign_internalis already somewhat entangled, so adding more to it just makes life harder... Will wait for feedback from Bruce.
I was thinking the opposite: this code is very similar to assign_internal and would be better placed there for ease of maintainance... ?
I am also wondering if removing values has other side effects, e.g. will this make \ifcsname false? That's not really possible in TeX, is it? (This has no real consequence of course since removeValue is only used for the box registers.)
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this code is very similar to assign_internal and would be better placed there for ease of maintainance... ?
Only if it can be DRY ("do not repeat yourself"). Otherwise just growing the body of the function will make it more impenetrable.
lib/LaTeXML/Core/State.pm
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| my @frames = @{ $$self{undo} }; | ||
| while (@frames) { | ||
| $frame = shift(@frames); | ||
| if (my $n = $$frame{value}{$key}) { # Undo the bindings, if $key was bound in this frame |
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Is this idempotent? I.e. if applied twice, will it remove the two previous bindings? That would be too much for \box.
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Curious idea - we don't yet have a test for that. Something like:
\newbox\myboxD
\setbox\myboxD\vbox{D won't appear outer.}
\begingroup
\setbox\myboxD\vbox{D will appear inner, once.}
\box\myboxD
\box\myboxD
\endgroup
\bye
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Added a test. It appears to work as expected?
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Scratch that, the test wasn't precise enough -- there is indeed a bug where unbinding twice will pop the outer frame, nice catch @xworld21
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Ok, using exists and a 0 value for the undo counter becomes idempotent. The new test now has correct timing and matches the PDF.
But the code got extra scary. Maybe good, maybe not?
Fixes #2412 .
Two key upgrades:
\copy\box, add a newremoveValuemethod in State, which (idempotently) unbinds the nearest binding of a value in the undo table.This gets the tests discussed in the issue to pass, and matches the pgf rendering in the PDF build (really great diagnostic by @xworld21 !)
I would need a second opinion by @brucemiller on whether this kind of "removeValue" method makes sense for latexml's State. Its code is inspired by the global assignment mode of
assign_internal, which will unbind all values in all frames, and then assign a value on the cleaned up 1-element stack.I am wondering if many of the current uses of
AssignValue($key, undef)are meant as thisRemoveValuebehavior, which could motivate changing local uses of assign_internal with undef to also unbind from the nearest assigned frame -- without creating a new method.Edit: Another direction for refining the code is to add a
'local'vs'global'argument forremoveValue, to indicate whether one or all bindings should be deleted.But I am feeling confident I am following the
\boxunbind semantics accurately now, as explained in the TeXbook. What was missing was unbinding the actual assignment - we were adding a local undef assignment, while also keeping the original assignment in place, when it happened in a higher frame.Thoughts?