Guide for parents with immutable elements #32353
Description
This ticket aims to solve the issue that arose in the thread
https://groups.google.com/g/sage-devel/c/DNrbtItMVmQ
(related tickets #29101, #30302, #30239, #23436, #14681, #13811, #19813) by implementing parents with immutable elements, which exist side by side with their twin parents with mutable elements.
The following table serves as a guide for the implementation:
| V=VectorSpace(R, 2, mutable=True) | new element | W=VectorSpace(R, 2, mutable=False) | new element |
|---|---|---|---|
| v, v | w, w' | ||
| v+v' | O | w+w' | |
| v+w, w+v | O | ||
| V(v) | O | W(w) | X |
| V(w) | O | W(v) | O |
| V(0) | O | W(0) | X |
| V.zero() | O | W.zero() | X |
| V([2,3]) | O | W([2,3]) | O |
| vector(v) | O | vector(w) | X |
| vector(R, 2) | O | ||
| vector(R, [2,3]) | O | vector(R, [2,3], mutable=False) | O |
| copy(v) | O | copy(w) | O |
| v.mutable() | X | w.immutable() | X |
| w.mutable() | O | v.immutable() | O |
| In the table, elements on the left belongs to V; elements on the right to W. |
Most parents in Sage have immutable elements and hence don't accept mutable argument. Parents that accept mutable argument defaults to mutable=True.
Parents that accept mutable argument are: VectorSpace, MatrixSpace, FreeModule, Graph
CC: @kliem @mjungmath @tscrim @egourgoulhon
Component: algebra
Issue created by migration from https://trac.sagemath.org/ticket/32353