Re: [Chicken-users] are standard bindings write protected?

[Felix Winkelmann]

Am 23 Nov 2003 13:33:38 +0100 hat Joerg F. Wittenberger 
<address@hidden> geschrieben:

> For clarification: I assumed that I would _import_ 'abort', 'force',
> 'signal', '##sys#error' etc. from the 'library' unit and just 'set!'
> the binding to a new value.  Should I really export those imported
> bindings to get the replaced globally?  I'd say that would be counter
> intuitive.

In a sense it is. `exporting' a variable means: use the global one,
shared by all code (through the symbol-table). If an identifier is not
exported, it will effectively be renamed.

> At least it raises the question (for me) how other (standard) units
> will behave.  Besides 'force' I'm replacing the exception handling
> mechanism and it would kill me if the standard units would not
> signaling their errors into my exception handler.

The current exception handler is global (via `(current-exception-handler)')
and it is explicitly meant for doing what you want. Replacing standard
procedures (like `force') may be a problem, since R5RS states that
redefinition of builtin procedures may not affect the behaviour of other
builtins.


cheers,
felix