It seems that there is a bug in unassign command of Release 4 when the argument is a table with indexing function.
> T:=table(symmetric); T := table(symmetric, [ ]) > T[1,2]:=10; T[1, 2] := 10 > T[1,3]:=20; T[1, 3] := 20
Let’s unassign one entry:
> unassign('T[1,3]'); Error, (in unknown) improper op or subscript selector
This bug is not present in Release 3.
It is a pity that new Maple releases produce bugs in procedures which were working correctly in previous versions.
Are the tests applied by Maple developers to new releases sharp enough?
The bug is removed with Maple V Release 5. (U. Klein)