(Basic Operations on Units): Mention exact versus inexact conversions.

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index d0b2860a3ae085460ce60955e38d2ef79ac7081e..f3ea32c158030688f2d97e815b7c90d6d250cd19 100644 (file)
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,11 @@
+2007-08-15  Jay Belanger  <jay.p.belanger@gmail.com>
+
+       * 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  <rgm@gnu.org>
 
        * mail/undigest.el (rmail-digest-parse-rfc1153sloppy): Be even

diff --git a/man/ChangeLog b/man/ChangeLog
index 648e3a104428cacc1a04b59c4d608cce898b285d..39f701981bad26e94eb0626b67ba219b16d5e19b 100644 (file)
--- a/man/ChangeLog
+++ b/man/ChangeLog
@@ -1,3 +1,8 @@
+2007-08-15  Jay Belanger  <jay.p.belanger@gmail.com>
+
+       * calc.texi (Basic Operations on Units): Mention exact versus
+       inexact conversions.
+
 2007-08-14  Jay Belanger  <jay.p.belanger@gmail.com>
 
        * calc.texi (Basic Operations on Units): Mention default

diff --git a/man/calc.texi b/man/calc.texi
index c2278639a87a7cfcb931a12f133074261ace5bdc..f21d1d3658287b3d79f7e174738b383a3cda36f4 100644 (file)
--- 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