Issue LCM-NO-ARGUMENTS Writeup

Issue:         LCM-NO-ARGUMENTS


References:    CLtL p. 202


Related issues: none


Category:      ADDITION


Edit history:  Version 1, Guy Steele 10/17/88


Problem description:


   CLtL incorrectly states that (lcm) should return infinity, and

   therefore specifies that giving lcm no arguments is an error.


   In point of mathematical fact, 1 is the identity for the lcm operation.


Proposal (LCM-NO-ARGUMENTS:1):  Define (lcm) to return the integer 1.


Examples:   (lcm) => 1


Test Cases:  (lcm) => 1


   Currently the behavior in this case is implementation-dependent.


Rationale:  Doing what is mathematically right.


Current practice:

   KCL signals an error.

   Lucid Lisp returns 1.

   Symbolics Common Lisp returns 1.


Cost to Implementors:  Pretty small (one-line fix).


Cost to Users:  None.


Cost of non-adoption:  Continued embarassment for Steele.


Performance impact:  Negligible.


Benefits:  Correct handling of a seldom-used boundary case.


Esthetics:  Mild improvement.


Discussion:  Mentioned in Steele's December 1985 "clarifications".