Re: When slots :type are used

* Raymond Toy <[email protected]> :
Wrote on Wed, 26 Nov 2008 17:08:56 -0500:

| Didier Verna wrote:

|> Section "2.23.2 Slot Type Checking" continues to puzzle me,
|> especially the fact that you have to be within *methods* for the
|> :type slot option to be taken in consideration when writing something

Which section is this?  I couldnt grep for this in the spec or mopspec.


|> to a slot. For instance, with:
|>
|> (defclass foo ()
|>   ((a :type fixnum)))
|>
|> (defvar *object* (make-instance 'foo))
|> (setf (slot-value *object* 'a) 3.5)    ;; this works like a charm
|>
|>
|> but: 
|>
|> (defmethod setslot ((foo foo) val)
|>     (setf (slot-value foo 'a) val))
|>
|> (setslot *object* 3.5) ;; triggers a type error
|>
|>
|> Can somebody provide a rationale for this ??
|>
|>
|>   
| Most likely because no got around to doing it.   Plus the most
| interesting/most common case is probably in a method.
|
| I'll see what I can do, but I know very little about the pcl
| implementation.

It may also have been a tradeoff, [since it is not being done in the
compiler] and you want to have at least one path available to the
programmer to set a slot value that avoids overhead of a type check.

--
Madhu