125 lines
4.0 KiB
Groff
125 lines
4.0 KiB
Groff
.\" $Id: units.1,v 1.6 1996/04/06 06:01:02 thorpej Exp $
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.TH UNITS 1 "14 July 1993"
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.SH NAME
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units - conversion program
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.SH SYNTAX
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.B units
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[-f filename] [-qv] [from-unit to-unit]
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.SH SUMMARY
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.TP 4
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.B -f filename
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Specifies the name of the units data file to load.
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.LP
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.TP 4
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.B -q
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Suppresses prompting of the user for units and the display of statistics
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about the number of units loaded.
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.LP
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.TP 4
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.B -v
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Prints the version number.
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.LP
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.TP 4
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.B from-unit to-unit
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Allows a single unit conversion to be done directly from the command
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line. No prompting will occur. The units program will print out
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only the result of this single conversion.
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.SH DESCRIPTION
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The units program converts quantities expression in various scales to
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their equivalents in other scales. The units program can only
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handle multiplicative scale changes. It cannot convert Centigrade
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to Fahrenheit, for example. It works interactively by prompting
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the user for input:
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.nf
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You have: meters
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You want: feet
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* 3.2808399
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/ 0.3048
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You have: cm^3
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You want: gallons
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* 0.00026417205
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/ 3785.4118
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.fi
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Powers of units can be specified using the '^' character as shown in
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the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'.
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Multiplication of units can be specified by using spaces, a dash or
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an asterisk. Division of units is indicated by the slash ('/').
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Note that multiplication has a higher precedence than division,
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so 'm/s/s' is the same as 'm/s^2' or 'm/s s'.
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If the user enters incompatible unit types, the units program will
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print a message indicating that the units are not conformable and
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it will display the reduced form for each unit:
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.nf
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You have: ergs/hour
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You want: fathoms kg^2 / day
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conformability error
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2.7777778e-11 kg m^2 / sec^3
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2.1166667e-05 kg^2 m / sec
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.fi
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.LP
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The conversion information is read from a units data file. The default
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file includes definitions for most familiar units, abbreviations and
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metric prefixes. Some constants of nature included are:
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.in +4m
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.ta
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.ta 9m +
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.nf
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pi ratio of circumference to diameter
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c speed of light
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e charge on an electron
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g acceleration of gravity
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force same as g
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mole Avogadro's number
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water pressure per unit height of water
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mercury pressure per unit height of mercury
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au astronomical unit
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.fi
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.in -4m
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\'Pound' is a unit of mass. Compound names are run together
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so 'poundforce' is a unit of force. British units that differ from their
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US counterparts are prefixed with 'br', and currency is prefixed with
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its country name: 'belgiumfranc', 'britainpound'. When searching for
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a unit, if the specified string does not appear exactly as a unit
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name, then the units program will try to remove a trailing 's' or
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a trailing 'es' and check again for a match.
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.LP
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All of these definitions can be read in the standard units file, or you
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can supply your own file. A unit is specified on a single line by
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giving its name and an equivalence. One should be careful to define
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new units in terms of old ones so that a reduction leads to the
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primitive units which are marked with '!' characters.
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The units program will not detect infinite loops that could be caused
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by careless unit definitions.
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.LP
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Prefixes are defined in the same was as standard units, but with
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a trailing dash at the end of the prefix name.
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.SH BUGS
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.LP
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The effect of including a '/' in a prefix is surprising.
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.LP
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Exponents entered by the user can be only one digit.
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You can work around this by multiplying several terms.
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.LP
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The user must use | to indicate division of numbers and / to
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indicate division of symbols. This distinction should not
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be necessary.
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.LP
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The program contains various arbitrary limits on the length
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of the units converted and on the length of the data file.
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.LP
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The program should use a hash table to store units so that
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it doesn't take so long to load the units list and check
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for duplication.
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.SH FILES
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/usr/share/misc/units.lib - the standard units library
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.SH AUTHOR
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Adrian Mariano (adrian@cam.cornell.edu or mariano@geom.umn.edu)
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