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simple-units

Very rudimentary support for the concept of quantity.

Documentation

Argument Conventions

OBJ is a Scheme object

NAME is a symbol

BASE-NAME is a symbol, the name of unit with the unit value of 1.

UNITS-NAME is a symbol

UNITS is an instance of units (Read as unit-set.)

UNITS-SYSTEM is an instance of units-system, the default is (default-units-system).

make-units

[syntax] (make-units NAME BASE-NAME [system: UNITS-SYSTEM] UNIT-SPEC...) => units
[syntax] (make-units NAME BASE-NAME [system: UNITS-SYSTEM] UNIT-SPEC...) => units
[syntax] (make-units* NAME BASE-NAME [system: UNITS-SYSTEM] UNIT-SPEC...) => units

UNIT-SPEC is the form <unit-spec>.

<unit-spec> := <unit-name> <unit-value>

<unit-value> ::= <unit-factor> <unit-value> ::= <unit-name> <unit-value> ::= (<unit-factor> <unit-name>)

<unit-name> ::= <symbol>

<unit-factor> ::= <number>

make-units* creates an anonymous units instance.

units?

[procedure] (units? OBJ) => boolean
[procedure] (check-units LOC OBJ [ARGNAM]) => *
[procedure] (error-units LOC OBJ [ARGNAM]

units-name

[procedure] (units-name UNITS) => symbol

units-base-name

[procedure] (units-base-name UNITS) => symbol

units-unit-names

[procedure] (units-unit-names UNITS) => (list-of symbol)

units-unit

[procedure] (units-unit UNITS NAME) => unit

Returns the unit with unit-name of NAME.

units-units-system

[procedure] (units-units-system UNITS) => units-system

The units-system defining UNITS.

make-quantity

[syntax] (make-quantity N NAME [UNITS]) => number
[syntax] (make-quantity N NAME [system: UNITS-SYSTEM]) => number
[syntax] (make-quantity N NAME UNITS-NAME system: UNITS-SYSTEM) => number

make-units-system

[procedure] (make-units-system NAME) => units-system

units-system?

[procedure] (units-system? OBJ) => boolean
[procedure] (check-units-system LOC OBJ [ARGNAM]) => *
[procedure] (error-units-system LOC OBJ [ARGNAM]

units-system-name

[procedure] (units-system-name [UNITS-SYSTEM]) => symbol

units-system-catalog

[procedure] (units-system-catalog [UNITS-SYSTEM]) => (list-of units)

units-system-units

[procedure] (units-system-units NAME [UNITS-SYSTEM]) => units

units-system-units/unit

[procedure] (units-system-units/unit NAME [UNITS-SYSTEM]) => units

default-units-system

[procedure] (default-units-system) => units-system
[procedure] (default-units-system UNITS-SYSTEM)

Gets and sets the default units-system.

unit?

[procedure] (unit? OBJ) => boolean
[procedure] (check-unit LOC OBJ [ARGNAM]) => *
[procedure] (error-unit LOC OBJ [ARGNAM])

unit-name

[procedure] (unit-name UNIT) => symbol

unit-factor

[procedure] (unit-factor UNIT) => number

units-scale

[procedure] (units-scale) => procedure
[procedure] (units-scale MULTIPLY) => procedure

MULTIPLY is a (procedure (number number) number).

Override when using the numbers extension, for example.

units-number?

[procedure] (units-number?) => procedure
[procedure] (units-number? PREDICATE) => procedure

PREDICATE is a (procedure (*) boolean).

Override when using the numbers extension, for example.

units-number-system

[procedure] (units-number-system MULTIPLY PREDICATE)

Convenience for units-scale & units-number?.

Usage

(require-extension simple-units)

Examples

(make-units time s
  m 60
  h (60 m)
  d (24 h)
  ms (0.0001 s)
  us (0.0001 ms))

(define 23h23m23s
  (+ (make-quantity 23 h)
     (make-quantity 23 m)
     (make-quantity 23 s)))
(define time-units
  (make-units* time s
    m 60
    h (60 m)
    d (24 h)
    ms (0.0001 s)
    us (0.0001 ms)))

(define 23h23m23s
  (+ (make-quantity 23 h time-units)
     (make-quantity 23 m time-units)
     (make-quantity 23 s time-units)))
(use numbers)

(units-number-system * number?) ;must override

(make-units time s
  m 60
  h (60 m)
  d (24 h)
  ms (1/1000 s)
  us (1/1000 ms))

(make-units distance m
  km 1000
  cm 1/100
  mm (1/10 cm)
  nm (1/1000 mm)

  yard 9144/10000 ; Defined in 1956
  foot (1/3 yard)
  inch (1/12 foot)
  mile (1760 yard)
  furlong (1/8 mile)

  fathom (2 yard) ; Defined in 1929
  nautical-mile 1852
  cable (1/10 nautical-mile)

  old-brit-nautical-mile ; Dropped in 1970
    (6080/3 yard)
  old-brit-cable
    (1/10 old-brit-nautical-mile)
  old-brit-fathom
    (1/100 old-brit-cable))

Notes

Requirements

format-compiler-base record-variants list-utils type-checks

Bugs and Limitations

This would be nice:

(define mile/h (make-derived-unit mile / h))
(define 23mile/h (make-quantity 23 mile/h))

Author

kon lovett

Version history

1.0.0
Hello.

License

Copyright (C) 2010 Kon Lovett. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.