Format conversion to floating point bug

[hunter@nlm.nih.gov (Larry Hunter)]

This one hurt:

    cl -qq
    Allegro CL 3.1.15.4 [Silicon Graphics Iris 4D] (9/18/90)

    ;; Copyright Franz Inc., Berkeley, CA, USA
    ;; Unpublished.  All rights reserved under the copyright laws
    ;; of the United States.

    ;; Restricted Rights Legend
    ;; ------------------------
    ;; Use, duplication, and disclosure by the Government are subject to
    ;; restrictions of Restricted Rights for Commercial Software developed
    ;; at private expense as specified in DOD FAR 52.227-7013 (c) (1) (ii).
    <cl> (format t "~4,2f" 1/21)
    Trace/BPT trap (core dumped)

This problem doesn't occur if the number used is 1/20.  I assume that the
problem is with repeating decimals or something like that.

Here are the implementation details:

    LISP-IMPLEMENTATION-TYPE: Allegro CL
    LISP-IMPLEMENTATION-VERSION: 3.1.15.4 [Silicon Graphics Iris 4D] (9/18/90)
    MACHINE-TYPE: Silicon Graphics Iris 4D
    MACHINE-VERSION: 
    SOFTWARE-TYPE: IRIX System V
    SOFTWARE-VERSION: 3.1
    SHORT-SITE-NAME: work
    *features*: (:COMPOSER :FAKE-ACTIVE-REGIONS :PCL :CLOS :BIG-ENDIAN :GSGC
     :ALLEGRO-V3.1 :FRANZ-INC :EXCL :ALLEGRO :COMMON-LISP :CONFORMING-IEEE :IEEE
     :FLAVORS :MIPS :R2000 :UNIX :SGI :SGI4D :IRIS4D :MULTIPROCESSING :CLX :XLIB
     :CLX-MIT-R4 :CLX-CL-ERROR :CW-X)
    *modules*: ("COMPOSER" "GPROF" "GR" "PROF" "TTYPROF" "MENU" "CLOS" "PCL" 
     "XVARS" "XCW" "XLIB" "CLX" "CLXEXCLDEP" "CSTRUCTS" "SIGIO" "ADVISE" "TRACE"
     "MDPROC" "PROCESS" "FOREIGN" "FOREIGN-FUNCTIONS" "QSTRUCTS")
    PATCH::*XCW-PATCHES*:
     (12 . "process interference caused text glitches on sgi")
     (11 . "bitblt fore/background colors")
     (10 . "'move' on the subwindow right button frame menu broke")
     (9 . "error when draw to a window while window manager is flushing it")
     (8 . "draw-polygon add closing line; draw-filled-polygon include last vertex")
     (7 . "don't ignore pre-initialize-cw open-font pixel-size arg")
    Allegro Composer: Composer Final 1.0.17.3 (6/25/90 20:00)
    disassmip: $Header: disassmip.cl,v 1.1 89/08/10 12:26:22 layer Rel $
    X Common Windows: X-CW 1.3.final.15.1 (6/25/90 20:00)
    cstructs: $Header: cstructs.cl,v 1.18 89/08/22 11:42:07 layer Rel $
    sigio: $Header: sigio.cl,v 1.3 89/08/24 14:03:01 layer Rel $
    trace: $Header: trace.cl,v 1.35 89/07/22 18:56:24 layer 

Hope you can fix this one quick!

Lawrence Hunter, PhD.
National Library of Medicine
Bldg. 38A, MS-54
Bethesda. MD 20894
(301) 496-9300
(301) 496-0673 (fax)
hunter@nlm.nih.gov (internet)