Package: units
Version: 1.85-3
Severity: normal
The man page explains why I have had some nasty bugs pop up in my
calculations:
Multiplication has a higher precedence than division and is evaluated
left to right, so
`m/s * s/day' is equivalent to `m / s s day' and has dimensions of
length per time cubed.
Similarly, `1/2 meter' refers to a unit of reciprocal length equivalent
to .5/meter, which
is probably not what you would intend if you entered that
expression. You can indicate
division of numbers with the vertical dash (`|'). This operator has the
highest precedence
so the square root of two thirds could be written `2|3^1|2'.
This is a poor choice, because algebraic notation says that division
has equal precedence to multiplication, and such operations are
performed left to right. This is the convention used in algebra,
algebraic calculators, and most computer languages.
See http://en.wikipedia.org/wiki/Order_of_operations
Since any such change is liable to break existing units scripts, it
might be wise to make use of a commandline switch or environment
variable to switch between the historical implementation and this, if
this were to be changed.
Cute:
You have: 2/3/4
You want:
Definition: 0.16666667
You have: 2/3*4
You want:
Definition: 0.16666667
-- System Information:
Debian Release: testing/unstable
APT prefers unstable
APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: i386 (i686)
Shell: /bin/sh linked to /bin/bash
Kernel: Linux 2.6.15.1
Locale: LANG=en_AU, LC_CTYPE=en_AU (charmap=ISO-8859-1)
Versions of packages units depends on:
ii libc6 2.3.6-3 GNU C Library: Shared libraries an
ii libncurses5 5.5-1 Shared libraries for terminal hand
ii libreadline5 5.1-6 GNU readline and history libraries
units recommends no packages.
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