HIDE

The HIDE function hides some levels of the stack to the rest of the executing code. This allows a kind of protection for levels which should not be accessed by a macro call for example. Note that this is not a real protection since a call to SHOW could reveal the hidden levels.

The hidden levels are always the deepest. Depending on the levels parameter to the call to HIDE, the hidden levels could be the whole stack (levels == 0), a maximum number of levels (levels >= 0) or a number of levels such that there remains at most a certain number ((abs(levels)) with levels < 0).

When called with NULL as parameter, HIDE will hide all the visible levels.

The number of newly hidden levels is returned.