Issue MACROEXPAND-HOOK-DEFAULT Writeup

Issue:        MACROEXPAND-HOOK-DEFAULT

Forum:	      Editorial

References:   MACROEXPAND (pp151-152), *MACROEXPAND-HOOK* (p152)

Category:     CLARIFICATION

Edit history: 02-Mar-91, Version 1 by Pitman

Status:	      For X3J13 consideration


Problem Description:


  In the description of the MACROEXPAND function on p152 of CLtL,

  it says ``The initial value of *MACROEXPAND-HOOK* is FUNCALL.''


  Does that mean the symbol FUNCALL, the function FUNCALL, or either?


Proposal (MACROEXPAND-HOOK-DEFAULT:EXPLICITLY-VAGUE):


  Specify that the initial value of *MACROEXPAND-HOOK* is either 

  the symbol FUNCALL or the function which it names.


Test Case:


  None.


Rationale:


  This leaves flexibility to an implementation which needs it to be

  #'FUNCALL for speed.  


Current Practice:


  In Symbolics Genera, the value is a function.


Cost to Implementors:


  None.


Cost to Users:


  None.


Cost of Non-Adoption:


  Lack of clear specification means mainly that implementors might worry

  they were doing the wrong thing if they use #'FUNCALL, but might worry

  about needless inefficiency if they use the symbol FUNCALL instead.


Benefits:


  Clearer specification.


Aesthetics:


  Negligible.


Discussion:


  Pitman doesn't care which way this is decided.