Rename get_exs in oper to get_deno

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add missing mixfix notation

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Uniform notation declarations.
Remove obsolete commands.
Simplify the elaborator

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Simplify the elaborator