Re: Issue: DISASSEMBLE-SIDE-EFFECT (version 2)

[Dan L. Pierson <pierson@mist>]

Issue:         DISASSEMBLE-SIDE-EFFECT
References:    DISASSEMBLE (p. 439), COMPILE (p. 439)
Category:      CLARIFICATION
Edit history:  Version 2 by Pierson 12/30/87
Status:        For Internal Discussion

Problem description:

The definition of DISASSEMBLE says that "if the relevant function is
not a compiled function, it is first compiled.".  The definition of
COMPILE says that "If name is a non-nil symbol, then the
compiled-function is installed as the global function definition of
the symbol...".  Several implementations have taken this to mean that
if DISASSEMBLE is passed a symbol which has an uncompiled function
definition, then it has the side-effect of (COMPILE 'symbol).

Proposal (DISASSEMBLE-SIDE-EFFECT:DO-NOT-INSTALL):

Clarify that when DISASSEMBLE compiles a function, it will never
install the newly compiled function.

Test Cases/Examples:

    (DEFUN F (A) (1+ A))
    (EQ (SYMBOL-FUNCTION 'F)
	(PROGN (DISASSEMBLE 'F)
	       (SYMBOL-FUNCTION 'F)))

This code will return T if this proposal is adopted.  Some current
implementations will return T, some will return NIL.

Rationale:

Several current implementations of DISASSEMBLE have surprising side
effects, especially for new users.

Current practice:

Allegro CL and Vax Lisp install the compiled definition.  Lucid,
Symbolics, Xerox, and KCL don't install it.  [[This is from an informal
survey at the last meeting; please correct any mistakes.]]

Cost to Implementors:

Some implementations will have to make a simple change.

Cost to Users:

Very little.  DISASSEMBLE is really part of the environment and is
probably not called by much, if any user code.

Cost of non-Adoption:

DISASSEMBLE will continue to surprise less experienced users.

Benefits:

DISASSEMBLE will become the predictable debugging function it was
meant to be.

Aesthetics:

Some who worried that DISASSEMBLE was supposed to install the compiled
function may find that the language has become a little cleaner.

Discussion: