1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
159 lines
4.8 KiB
Groff
159 lines
4.8 KiB
Groff
.\" $FreeBSD$
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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] [-q] [to-unit from-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 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. The program will not print prompts. It will print out the
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result of the single specified conversion.
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.SH DESCRIPTION
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The units program converts quantities expressed 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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You have: meters/s
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You want: furlongs/fortnight
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* 6012.8848
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/ 0.00016630952
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You have: 1|2 inch
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You want: cm
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* 1.27
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/ 0.78740157
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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'. Division of numbers
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must be indicated using the vertical bar ('|'). To convert half a
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meter, you would write '1|2 meter'. If you write '1/2 meter' then the
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units program would interpret that as equivalent to '0.5/meter'.
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If you enter 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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The unit 'pound' is a unit of mass. Compound names are run together
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so 'poundforce' is a unit of force. The unit 'ounce' is also a unit
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of mass. The fluid ounce is 'floz'. British units that differ from
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their US counterparts are prefixed with 'br', and currency is prefixed
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with its country name: 'belgiumfranc', 'britainpound'. When searching
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for 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 a
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trailing 'es' and check again for a match.
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.LP
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To find out what units are available read the standard units file.
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If you want to add your own units you can supply your own file.
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A unit is specified on a single line by
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giving its name and an equivalence. 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. Comments in the unit definition file
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begin with a '/' character at the beginning of a line.
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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. If a unit is not found
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even after removing trailing 's' or 'es', then it will be checked
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against the list of prefixes. Prefixes will be removed until a legal
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base unit is identified.
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.LP
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Here is an example of a short units file that defines some basic
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units.
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.in 17m
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.ta
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.ta 9m +
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.nf
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m !a!
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sec !b!
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micro- 1e-6
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minute 60 sec
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hour 60 min
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inch 0.0254 m
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ft 12 inches
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mile 5280 ft
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.fi
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.in -17m
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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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units.lib - the standard units library
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.SH AUTHOR
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Adrian Mariano (adrian@cam.cornell.edu)
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