Package "units"

Title:	unit and quantity arithmetic for swi-prolog
Rating:	Not rated. Create the first rating!
Latest version:	0.4
SHA1 sum:	006ebf96f542bcd26605dc33b0b92b2a4af5f02a
Author:	Kwon-Young Choi <kwon-young.choi@hotmail.fr>
Maintainer:	Kwon-Young Choi <kwon-young.choi@hotmail.fr>
Packager:	Kwon-Young Choi <kwon-young.choi@hotmail.fr>
Home page:	https://github.com/kwon-young/units
Download URL:	https://github.com/kwon-young/units/releases/*.zip
Requires:	prolog>=9.3.15
Provides:	units

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Version	SHA1	#Downloads	URL
0.4	006ebf96f542bcd26605dc33b0b92b2a4af5f02a	5	https://github.com/kwon-young/units
0.3	6205801eb7c3db36af683b73af6b3bcf96e89bd5	4	https://github.com/kwon-young/units
0.1	8fbf439a214a72b82623dfdc5d69782318c83860	1	https://github.com/kwon-young/units

Units: Quantity and Units library for swi-prolog

Units is a quantity and units library modeled after mp-units.

Here is a quick preview of what is possible:

:- use_module(library(units)).

% simple numeric operations
?- qeval(10*km =:= 2*5*km).

% conversions to common units
?- qeval(1 * h =:= 3600 * s).
?- qeval(1 * km + 1 * m =:= 1001 * m).

% derived quantities
?- qeval(1 * km / (1 * s) =:= 1000 * m / s).
?- qeval(2 * km / h * (2 * h) =:= 4 * km).
?- qeval(2 * km / (2 * km / h) =:= 1 * h).

?- qeval(2 * m * (3 * m) =:= 6 * m^2).

?- qeval(10 * km / (5 * km) =:= 2).

?- qeval(1000 / (1 * s) =:= 1 * kHz).

% assignement and comparison
?- qeval(A is 10*m), qeval(A < 20*km).
A = 10 * kind(isq:length)[si:metre].

The library can be used through a single predicate qeval/1 which is a predicate that wraps any kind of arithmetic operations.

One of the specificity of the library is the combination of units and quantities. Please read the excellent mp-units documentation on the advantages of using quantities in addition to units.

Units and quantites can be used in multiple ways:

• for units
  • System:Unit, example: si:metre. Currently, the si and international system are implemented.
  • System:UnitSymbol, example: si:m for si:metre.
  • Unit, example: metre
  • UnitSymbol, example: m for si:metre
  • `System:Prefix(Unit)`, example: si:kilo(metre)
  • `System:Prefix(OtherSystem:Unit)`, example: si:kilo(international:pound_force)
  • `Prefix(Unit)`, example: kilo(metre)
  • PrefixSymbolUnitSymbol, example: km for kilo(metre)
  • through aliases, but only a few are defined like kilogram for si:kilo(gram) or hectare for si:hecto(are)
• for quantities
  • System:Quantity, example: isq:length. isq is the only system of quantity implemented.
• for both at the same time
  • `Quantity[Unit]`, example: `isq:length[si:metre]`

  Here is a interesting use of the speed quantity that can be use to generically describe the ratio of any type of length by any type of time:

  :- use_module(library(units)).
  
  avg_speed(Distance, Time, Speed) :-
     qeval(S is Distance / Time),
     Speed = S.as(isq:speed).
  
  ?- avg_speed(220 * isq:distance[si:kilo(metre)], 2 * si:hour, Speed),
     qmust_be(isq:speed[si:kilo(metre)/si:hour], Speed).
  Speed = 110 * isq:speed[si:kilo(metre)/si:hour].
  
  ?- avg_speed(220 * isq:height[inch], 2 * si:second, Speed).
  Speed = 110 * isq:speed[international:inch/si:second].
  
  ?- avg_speed(220 * si:gram, 2 * si:second, Speed).
  ERROR: Domain error: `kind(isq:mass)/kind(isq:time)' expected, found `isq:speed'

  The qmust_be/2 predicate can be used to check the quantity and unit of a result.

clpBNR support

One peculiar feature is that this library also supports clpBNR arithmetic:

?- qeval({A*metre == B*inch}), A = 1.
A = 1,
B = 5000r127.

Contents of pack "units"

Pack contains 11 files holding a total of 74.7K bytes.