Substitutions inside piecewise functions don't work

[rwst]

Not implemented at the moment

sage: f = piecewise([((0,1), x^2), ([-1,0], -x)], var=x);
sage: f.subs(x=-1)
1
sage: f.subs(x=y)
...
ValueError: substituting the piecewise variable must result in real number

Component: symbolics

Author: Ralf Stephan

Branch/Commit: u/rws/substitutions_inside_piecewise_functions_don_t_work @ 98cab8b

Issue created by migration from https://trac.sagemath.org/ticket/22102

[rwst]

comment:1

It may be desirable to substitute inside the piece expressions only, and require the user to generate a new function for a variable change.

[rwst]

Branch: u/rws/substitutions_inside_piecewise_functions_don_t_work

[rwst]

Author: Ralf Stephan

[rwst]

New commits:

98cab8b

22102: remove restrictions in piecewise._subs_

[rwst]

Commit: 98cab8b

[rwst]

comment:4

#21071 requires a different approach.

[fchapoton]

see #38706 for some progress