[Maxima-bugs] [maxima:bugs] Re: #4749 Declaring a symbol both real and complex or real and imaginary

[David S. <tom...@us...>]

I like your pragmatic definition.
We should extend `risplit` so that it can raise errors (controlled by a flag) for expressions that do not describe real or complex numbers, for example `true`, `false`, `und`, `ind`, `inf`, `minf`, lists, equations, inequalities, sets, matrices, ...
Then we can safely rely on `risplit` in `$featurep`.


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**[bugs:#4749] Declaring a symbol both real and complex or real and imaginary**

**Status:** maybe-fixed
**Group:** None
**Labels:** declare rectform featurep csign 
**Created:** Mon Jun 01, 2026 07:19 AM UTC by David Scherfgen
**Last Updated:** Tue Jun 02, 2026 07:03 AM UTC
**Owner:** nobody


Maxima allows declaring a symbol both `real` and `complex` and even both `real` and `imaginary`. I think that in the second case, it should at least issue a warning, if not an error.

For the first case, where a symbol is declared both `real` and `complex`, Maxima behaves differently across `csign`, `rectform` and `featurep`:

~~~
(%i1) declare(x, real, x, complex);
(%o1) done

(%i2) csign(x);
(%o2) complex

(%i3) rectform(x);
(%o3) x

(%i4) featurep(x, real);
(%o4) true

(%i5) featurep(x, complex);
(%o5) true
~~~

These functions all have a different concept ...


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