Package: clisp Version: 1:2.41-1 Severity: normal Hi, I'm trying to compare a floating-point number and a rational. According to the rule of float and rational contagion, described in CLHS 12.1.4.1, and X3J13 issue CONTAGION-ON-NUMERICAL-COMPARISONS:TRANSITIVE, such a comparison should always return the mathematically correct result, as if the floating-point number were first converted to a rational with RATIONAL. Instead, CLISP signals an underflow condition: $ clisp -q -x '(< (expt 10 -100) least-positive-short-float)' *** - floating point underflow The Implementation Notes for GNU CLISP, sections 12.2.3.1 and 12.2.3.2, don't seem to say anything about comparisons, but mention two variables which control ANSI-compliance. CLISP behaves the same when invoked with "-ansi", to set these and any similar variables to T. $ clisp -ansi -q -x '(< (expt 10 -100) least-positive-short-float)' *** - floating point underflow This X3J13 issue is listed as supported in the Implementation Notes for GNU CLISP: http://clisp.cons.org/impnotes.html#issues CLISP behaves as expected if the floating-point number is filtered through RATIONAL. (Note that CLHS 12.1.4.1 explicitly states "When rationals and floats are compared by a numerical function, the function rational is effectively called to convert the float to a rational and then an exact comparison is performed.") $ clisp -q -x '(< (expt 10 -100) (rational least-positive-short-float))' T $ clisp -q -x '(< (expt 10 -10) (rational least-positive-short-float))' NIL I'm fairly certain CLISP is in error. Thanks, -- System Information: Debian Release: 4.0 APT prefers stable APT policy: (500, 'stable') Architecture: amd64 (x86_64) Shell: /bin/sh linked to /bin/bash Kernel: Linux 2.6.18-12-custom-xen-ws-1 Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) Versions of packages clisp depends on: ii common-lisp-controller 6.9 This is a Common Lisp source and c ii libc6 2.3.6.ds1-13 GNU C Library: Shared libraries ii libice6 1:1.0.1-2 X11 Inter-Client Exchange library ii libncurses5 5.5-5 Shared libraries for terminal hand ii libreadline5 5.2-2 GNU readline and history libraries ii libsm6 1:1.0.1-3 X11 Session Management library ii libx11-6 2:1.0.3-7 X11 client-side library ii libxext6 1:1.0.1-2 X11 miscellaneous extension librar ii libxpm4 1:3.5.5-2 X11 pixmap library clisp recommends no packages. -- no debconf information -- J.P. Larocque: <piranha@thoughtcrime.us>, <piranha@ely.ath.cx>