[Maxima-bugs] [maxima:bugs] #4629 box expression missing simp flags & expand applied to boxed objects

[Robert D. <rob...@us...>]

- **labels**:  --> box, expand, simplification



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**[bugs:#4629] box expression missing simp flags & expand applied to boxed objects**

**Status:** open
**Group:** None
**Labels:** box expand simplification 
**Created:** Tue Nov 04, 2025 12:45 PM UTC by Barton Willis
**Last Updated:** Tue Nov 04, 2025 12:45 PM UTC
**Owner:** nobody


The user documentation doesn't say what `expand` is supposed to do to a boxed expression, but I'm pretty sure that we don't want `expand` to strip a boxed expression of some of its `simp` flags:

~~~
(%i25) xxx : box(x/2)$

(%i26) ?print([xxx,expand(xxx)]);

((MLIST SIMP) ((MBOX) ((MTIMES SIMP) ((RAT SIMP) 1 2) $X))
                                        ((MBOX) ((MTIMES) ((RAT) 1 2) $X)))
~~~
In the expanded expression, `rat` lost its  `simp` flag. Additionally,  the `mbox` operators are missing a `simp` flag.

For a labeled box, all is well:
~~~
(%i32) xxx : box(x/2,0)$

(%i33) ?print([xxx,expand(xxx)]);

((MLIST SIMP) ((MLABOX SIMP) ((MTIMES SIMP) ((RAT SIMP) 1 2) $X) 0)
                                        ((MLABOX SIMP) ((MTIMES SIMP) ((RAT SIMP) 1 2) $X) 0))
(%o33) [box(x/2,0),box(x/2,0)]
~~~

This was done with a recent Maxima build. With Maxima 5.48.1, I think all is well:

~~~
(%i1)	xxx : box(x/2);
(xxx)	box(x/2)
(%i2)	?print(%);
((MBOX SIMP) ((MTIMES SIMP) ((RAT SIMP) 1 2) $X)) 

(%o2)	box(x/2)
(%i3)	expand(xxx);
(%o3)	box(x/2)
(%i4)	?print(%);
((MBOX SIMP) ((MTIMES SIMP) ((RAT SIMP) 1 2) $X)) 

(%o4)	box(x/2)
~~~




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