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Documentation

Rudimentary support for the concept of quantity.

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).

Units (Unit-Set)

make-units

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

Returns a new units.

Also pollutes the UNITS-SYSTEM with the new units, unless it already exists by-name. In which case the new units is said to be standalone.

NAME is a symbol, the name of the units.

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

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*

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

Like make-units but always creates an standalone units instance, i.e. the UNITS-SYSTEM is not polluted by the created units.

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-factor

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

Returns the value for the unit with NAME in UNITS

units-units-system

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

The units-system defining UNITS.

Quantity

quantity

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

make-quantity

[procedure] (make-quantity N NAME UNITS) => number

Units System

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

Returns the units of NAME in the UNITS-SYSTEM.

units-system-units/unit

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

Returns the units with unit of NAME in the UNITS-SYSTEM.

units-system-add-units!

[procedure] (units-system-add-units! UNITS [UNITS-SYSTEM])

Adds UNITS to UNITS-SYSTEM catalog, replacing any existing units of the same name.

default-units-system

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

Gets and sets the default units-system.

Unit

factor?

[procedure] (factor? OBJ) => boolean

Is OBJ a factor, as determined by (units-number-predicate)?

[procedure] (check-factor LOC OBJ [ARGNAM]) => *
[procedure] (error-factor LOC OBJ [ARGNAM])

units-factor-scale

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

Gets and sets the procedure used to scale factors.

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

Override when using the numbers extension, for example.

units-number-predicate

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

Gets and sets the procedure used determine what is a number.

PREDICATE is a (procedure (*) boolean).

Override when using the numbers extension, for example.

units-number-system

[procedure] (units-number-system MULTIPLY PREDICATE)
[procedure] (units-number-system) => (values procedure procedure)

Convenience for units-factor-scale & units-number-predicate?. When no arguments returns 2 values, the (units-factor-scale) and (units-number-predicate?).

Usage

(require-extension simple-units)

Examples

Using a registerd units

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

(define 23h23m23s
  (+ (quantity 23 h)
     (quantity 23 m)
     (quantity 23 s)))

Using a standalone units

(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
  (+ (quantity 23 h time-units)
     (quantity 23 m time-units)
     (quantity 23 s time-units)))

Using numbers.

(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)

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

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

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

Requirements

record-variants list-utils symbol-utils lookup-table moremacros type-checks

setup-helper

Bugs and Limitations

A unit is not 1st-class.
A quantity is not 1st-class. Requires extending the numeric tower!
No dimension concept.
Cannot remove a units from a units-system.
Cannot extend a units, only re-define.
The units-factor-scale & units-number-predicate variables are a kludge.
Cannot create derived units.

Version history

1.2.4: New distributed egg repository system cannot update existing release.
1.2.3: Added variable-item dependency.
1.2.2: Update dependencies, fix version number.
1.2.1: Update dependencies.
1.2.0: Removed dependency on "format-compiler-base".
1.1.0
1.0.0: Hello.

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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.