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Issue DISASSEMBLE-SIDE-EFFECT Writeup

Issue:         DISASSEMBLE-SIDE-EFFECT

References: DISASSEMBLE (p. 439), COMPILE (p. 439)

Category: CLARIFICATION

Edit history: Version 2 by Pierson 12/30/87

Version 3 by Pierson 1/21/88

Version 4 by Pierson 6/10/88 correct VAX Lisp practice

Status: Ready For Release?

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 installs the compiled definition. Lucid, Symbolics, Xerox,

VAX Lisp, and KCL don't install it.

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:

DISASSEMBLE is an environment feature; some question has been raised

as to the place and force of environment features in the standard.

However, this proposal stands if DISASSEMBLE is part of the standard

language.


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