substitution in expression
After reading Simplify shenanigans, I am very confused about the possibility of doing
sage: sin(x).subs(sin(x) == 3) 3
Which becomes even more funny with
sage: SR(2).subs(SR(2) == pi) pi
I thought one may only set values to variable but no: I can set value to integers !
Is there a concrete example where this is useful ? Or this is just one more argument to avoid the use of the symbolic ring ?
Anyway the substitution is not at all consistent with the behavior of the symbolic ring. If such substitutions are allowed, then the expression
SR(2) + SR(2) should not be simplified !