Module Name: src
Committed By: dholland
Date: Sun Apr 3 19:44:15 UTC 2011
Modified Files:
src/usr.bin/units: units.1
Log Message:
Expand user warning (adding examples) and move to CAVEATS as it's not fixable.
To generate a diff of this commit:
cvs rdiff -u -r1.16 -r1.17 src/usr.bin/units/units.1
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/units/units.1
diff -u src/usr.bin/units/units.1:1.16 src/usr.bin/units/units.1:1.17
--- src/usr.bin/units/units.1:1.16 Sun Apr 3 19:25:05 2011
+++ src/usr.bin/units/units.1 Sun Apr 3 19:44:15 2011
@@ -1,5 +1,5 @@
-.\" $NetBSD: units.1,v 1.16 2011/04/03 19:25:05 dholland Exp $
-.Dd March 28, 2011
+.\" $NetBSD: units.1,v 1.17 2011/04/03 19:44:15 dholland Exp $
+.Dd April 3, 2011
.Dt UNITS 1
.Os
.Sh NAME
@@ -159,6 +159,32 @@
.An Adrian Mariano Aq adr...@cam.cornell.edu
or
.Aq mari...@geom.umn.edu
+.Sh CAVEATS
+While
+.Nm
+can be used as a calculator for many unit-related computations,
+caution is required: many computations require additional constant
+factors deriving from the physics (or chemistry or whatever) of the
+situation.
+As these factors are dimensionless,
+.Nm
+cannot itself either provide them or warn the user when they have been
+forgotten.
+For example, one joule is one kilogram meter squared per second
+squared, by definition; however, the kinetic energy of a one-kilogram
+object moving at one meter per second is half a joule, not one joule,
+because of a dimensionless factor that arises from integration.
+.Pp
+Also, some pairs of units that have the same dimensionality are
+nonetheless used to measure different things and attempting to convert
+between them may require additional fudge factors or be entirely
+meaningless.
+For example, torque and energy have the same dimensionality, but
+attempting to convert torque in newton-meters to energy in joules is
+nonsensical.
+There is no practical way for
+.Nm
+to warn about these issues either.
.Sh BUGS
The effect of including a
.Sq \&/
@@ -180,6 +206,3 @@
The program should use a hash table to store units so that
it doesn't take so long to load the units list and check
for duplication.
-.Pp
-The program should warn users when they're trying to perform a conversion
-that doesn't make sense, since there are many such combinations.
