From: Jay Belanger Date: Wed, 15 Aug 2007 15:47:45 +0000 (+0000) Subject: (Basic Operations on Units): Mention exact versus inexact conversions. X-Git-Tag: emacs-pretest-23.0.90~11497 X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=42964ef859eef3aeb1e31f62a34b2e3ead9103e0;p=emacs.git (Basic Operations on Units): Mention exact versus inexact conversions. --- diff --git a/lisp/ChangeLog b/lisp/ChangeLog index d0b2860a3ae..f3ea32c1580 100644 --- a/lisp/ChangeLog +++ b/lisp/ChangeLog @@ -1,3 +1,11 @@ +2007-08-15 Jay Belanger + + * calc/calc-units.el (math-standard-units): Update values. + Put in exact, rational values when possible. + (math-unit-prefixes): Replace floats with powers of ten. + (math-standard-units-systems): Replace floats with integers. + (math-make-unit-string): Remove extra spaces in output. + 2007-08-15 Glenn Morris * mail/undigest.el (rmail-digest-parse-rfc1153sloppy): Be even diff --git a/man/ChangeLog b/man/ChangeLog index 648e3a10442..39f701981ba 100644 --- a/man/ChangeLog +++ b/man/ChangeLog @@ -1,3 +1,8 @@ +2007-08-15 Jay Belanger + + * calc.texi (Basic Operations on Units): Mention exact versus + inexact conversions. + 2007-08-14 Jay Belanger * calc.texi (Basic Operations on Units): Mention default diff --git a/man/calc.texi b/man/calc.texi index c2278639a87..f21d1d36582 100644 --- a/man/calc.texi +++ b/man/calc.texi @@ -27443,6 +27443,14 @@ the above example, entering the units expression @samp{100 km/hr} and typing @kbd{u c @key{RET}} (without specifying new units) produces @samp{27.7777777778 m/s}. +While many of Calc's conversion factors are exact, some are necessarily +approximate. If Calc is in fraction mode (@pxref{Fraction Mode}), then +unit conversions will try to give exact, rational conversions, but it +isn't always possible. Given @samp{55 mph}, typing +@kbd{u c m/s @key{RET}} produces @samp{15367:625 m/s}, for example, +while typing @kbd{u c au/yr @key{RET}} produces +@samp{5.18665819999e-3 au/yr}. + If the units you request are inconsistent with the original units, the number will be converted into your units times whatever ``remainder'' units are left over. For example, converting @samp{55 mph} into acres