Issue CONDITION-ACCESSORS-SETFABLE Writeup

Issue:		CONDITION-ACCESSORS-SETFABLE

Forum:		Cleanup

References:	Condition System, version 18

Category:	CLARIFICATION

Edit History:	Version 1, 1/3/90 by Kim A. Barrett


Problem Description:

  It is presently unspecified whether the accessor functions defined for the

  various standard condition classes may be used as places for SETF.


Proposal (CONDITION-ACCESSORS-SETFABLE:NO):

  The effect of using accessor functions defined for the various standard

  (i.e., pre-defined) condition classes as places for SETF is undefined.


Rational:

  Conditions are used to record state at a particular point in time.  Allowing

  them to be modified at some later time makes little sense.  The Condition

  System does say that it is an error to attempt to assign a condition's slots

  by using SETF.


Current Practice:

  IIM does not make these functions be setfable.


Cost to Implementors:

  Implementations might want to change all the DEFINE-CONDITIONs to use

  :READER rather than :ACCESSOR when defining the accessor methods on the

  slots is fairly trivial--however technically this issue itself does not

  force the need for that change.  Fixing any code which currently depends

  on being able to SETF one of these accessors might be more work in some

  implementations.


Cost to Users:

  Programs which currently depend on being able to SETF these accessors are

  already non-portable.


Benifits:

  Users will know what to expect.


Discussion:

  Pitman and Barrett supports proposal NO.