c706c470e4
- notionally support a 'history file' flag. This doesn't do much now, but is there to prevent scripts written against GNU units from breaking - correctly gracefully quit rather than exit (this will make it easier to support a history file in the future) - remove the "t" flag from fopen which was there to support windows. We have not supported windows since at the latest, the introduction of capsicum.
206 lines
5.9 KiB
Groff
206 lines
5.9 KiB
Groff
.\" $FreeBSD$
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.Dd July 4, 2014
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.Dt UNITS 1
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.Os
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.Sh NAME
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.Nm units
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.Nd conversion program
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.Sh SYNOPSIS
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.Nm
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.Op Fl f Ar filename
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.Op Fl H Ar filename
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.Op Fl qvUV
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.Op Ar from-unit to-unit
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.Sh OPTIONS
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The following options are available:
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.Bl -tag -width indent
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.It Fl h No , Fl -help
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Show an overview of options
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.It Fl f Ar filename No , Fl -file Ar filename
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Specify the name of the units data file to load.
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.It Fl H Ar filename No , Fl -historyfile Ar filename
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Ignored, for compatibility with GNU units.
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.It Fl e , Fl -exponential
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Behave as if -o '%6e' was typed.
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.It Fl q No , Fl -quiet
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Suppress 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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.It Fl U No , Fl -unitsfile
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If the default unit file exists prints its location.
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If not, print
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.Qo
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Units data file not found
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.Qc
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.It Fl t No , Fl -terse
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Only print the result. This is used when calling
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.Nm
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from other programs for easy to parse results.
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.It Fl v No , Fl -verbose
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Print the units in the conversion output.
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Be more verbose in general.
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.It Fl o Ar format No , Fl -output-format Ar format
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Select the output format string by which numbers are printed.
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.It Fl V No , Fl -version
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Print the version number, usage, and then exit.
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.It Ar from-unit to-unit
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Allow a single unit conversion to be done directly from the command
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line.
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The program will not print prompts.
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It will print out the
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result of the single specified conversion.
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.El
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.Sh DESCRIPTION
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The
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.Nm
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program converts quantities expressed in various scales to
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their equivalents in other scales.
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The
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.Nm
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program can only
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handle multiplicative or affine scale changes.
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It works interactively by prompting
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the user for input:
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.Bd -literal
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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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You have: 85 degF
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You want: degC
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29.444444
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.Ed
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.Pp
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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.
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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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Division of numbers
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must be indicated using the vertical bar ('|').
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To convert half a
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meter, you would write '1|2 meter'.
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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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.Bd -literal
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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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.Ed
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.Pp
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The conversion information is read from a units data file.
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The default
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file includes definitions for most familiar units, abbreviations and
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metric prefixes.
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Some constants of nature included are:
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.Pp
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.Bl -column -offset indent -compact "mercury"
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.It "pi ratio of circumference to diameter"
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.It "c speed of light"
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.It "e charge on an electron"
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.It "g acceleration of gravity"
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.It "force same as g"
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.It "mole Avogadro's number"
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.It "water pressure per unit height of water"
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.It "mercury pressure per unit height of mercury"
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.It "au astronomical unit"
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.El
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.Pp
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The unit 'pound' is a unit of mass.
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Compound names are run together
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so 'pound force' is a unit of force.
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The unit 'ounce' is also a unit
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of mass.
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The fluid ounce is 'floz'.
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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'.
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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
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.Nm
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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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.Pp
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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.
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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
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.Nm
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program will not detect infinite loops that could be caused
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by careless unit definitions.
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Comments in the unit definition file
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begin with a '#' or '/' character at the beginning of a line.
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.Pp
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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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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.
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Prefixes will be removed until a legal
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base unit is identified.
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.Pp
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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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.Pp
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.Bl -column -offset indent -compact "minute"
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.It "m !a!"
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.It "sec !b!"
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.It "micro- 1e-6"
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.It "minute 60 sec"
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.It "hour 60 min"
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.It "inch 0.0254 m"
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.It "ft 12 inches"
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.It "mile 5280 ft"
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.El
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.Sh FILES
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.Bl -tag -width /usr/share/misc/definitions.units -compact
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.It Pa /usr/share/misc/definitions.units
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the standard units library
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.El
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.Sh AUTHORS
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.An Adrian Mariano Aq Mt adrian@cam.cornell.edu
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.Sh BUGS
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The effect of including a '/' in a prefix is surprising.
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.Pp
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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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.Pp
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The user must use | to indicate division of numbers and / to
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indicate division of symbols.
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This distinction should not
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be necessary.
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.Pp
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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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.Pp
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The program should use a hash table to store units so that
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it does not take so long to load the units list and check
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for duplication.
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