forked from mpusz/mp-units
563b358d5e
Dimensionless quantities are now represented by quantity types rather than by plain representation types. Only dimensionless quantities with `unitless` unit are implicitly convertible from representation types. `units::exp()` now is a function doing std::exp() on a representation type (previous `units::exp` class template was renamed to `units::exponent`). BREAKING_CHANGE: gcc-9.3 support removed BREAKING_CHANGE: `exp` and `Exp` renamed to `exponent` and `Exponent` Resolves #27 Resolves #42
42 lines
1.2 KiB
ReStructuredText
42 lines
1.2 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`, and `QuantityPoint`:
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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>Unit]<-[Dimension]
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[Dimension]<-[Quantity]
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[Unit]<-[Quantity]
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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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