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67 lines
1.9 KiB
ReStructuredText
67 lines
1.9 KiB
ReStructuredText
.. namespace:: units
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Basic Concepts
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==============
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The most important concepts in the library are `Unit`, `Dimension`,
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`Quantity`, `QuantityPoint`, `QuantityKind`, and `QuantityPointKind`:
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.. image:: /_static/img/concepts.png
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:align: center
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..
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http://www.nomnoml.com
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[<abstract>Dimension|
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[base_dimension<Symbol, Unit>]<-[exponent<Dimension, Num, Den>]
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[derived_dimension<Child, Unit, Exponent...>]<-[exponent<Dimension, Num, Den>]
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[exponent<Dimension, Num, Den>]<-[derived_dimension<Child, Unit, Exponent...>]
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]
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[<abstract>Quantity|
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[quantity<Dimension, Unit, Rep>]
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]
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[<abstract>QuantityPoint|
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[quantity_point<Dimension, Unit, Rep>]
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]
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[<abstract>QuantityKind|
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[quantity_kind<Kind, Unit, Rep>]
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]
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[<abstract>QuantityPointKind|
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[quantity_point_kind<PointKind, Unit, Rep>]
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]
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[<abstract>Unit]<-[Dimension]
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[Dimension]<-[Quantity]
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[Unit]<-[Quantity]
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[Quantity]<-[QuantityPoint]
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[<abstract>Kind]<-[QuantityKind]
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[Dimension]<-[Kind]
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[Quantity]<-[QuantityKind]
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[<abstract>PointKind]<-[QuantityPointKind]
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[Kind]<-[PointKind]
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[QuantityKind]-<[QuantityPointKind]
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`Unit` is a basic building block of the library. Every dimension works with
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a concrete hierarchy of units. Such hierarchy defines a reference unit and
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often a few scaled versions of it.
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`Dimension` concept matches a dimension of either a base or derived quantity.
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`base_dimension` is instantiated with a unique symbol identifier and a base
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unit. `derived_dimension` is a list of exponents of either base or other
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derived dimensions.
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`Quantity` is a concrete amount of a unit for a specified dimension with a
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specific representation.
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`QuantityPoint` is an absolute `Quantity` with respect to some origin.
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`QuantityKind` is a `Quantity` with more specific usage.
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`QuantityPointKind` is an absolute `QuantityKind` with respect to some origin.
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