forked from mpusz/mp-units
118 lines
3.8 KiB
ReStructuredText
118 lines
3.8 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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.. raw:: html
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<object data="../_images/concepts.svg" type="image/svg+xml" class="align-center" style="max-width: 100%;"></object>
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..
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https://www.planttext.com
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@startuml
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skinparam monochrome true
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skinparam shadowing false
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skinparam backgroundColor #fcfcfc
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hide circle
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hide members
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show class methods
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package Unit <<Frame>> [[../../framework/units.html]] {
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}
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package Dimension <<Frame>> [[../../framework/dimensions.html]] {
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}
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package Kind <<Frame>> [[../../framework/quantity_kinds.html#kind-creation]] {
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abstract kind<Dimension> [[../../framework/quantity_kinds.html#kind-creation]]
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}
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package PointKind <<Frame>> [[../../framework/quantity_kinds.html#quantity-point-kinds]] {
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abstract point_kind<Kind, PointOrigin> [[../../framework/quantity_kinds.html#quantity-point-kinds]]
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}
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package PointOrigin <<Frame>> [[../../framework/quantity_points.html#point-origins]] {
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abstract point_origin<Dimension> [[../../framework/quantity_points.html#point-origins]]
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}
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package Quantity <<Frame>> [[../../framework/quantities.html]] {
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class quantity<Dimension, Unit, Rep> [[../../framework/quantities.html#construction]] {
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rep number()
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}
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}
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package QuantityPoint <<Frame>> [[../../framework/quantity_points.html]] {
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class quantity_point<PointOrigin, Unit, Rep> [[../../framework/quantity_points.html#construction]] {
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quantity relative()
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}
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}
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package QuantityKind <<Frame>> [[../../framework/quantity_kinds.html]] {
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class quantity_kind<Kind, Unit, Rep> [[../../framework/quantity_kinds.html#construction]] {
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quantity common()
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}
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}
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package QuantityPointKind <<Frame>> [[../../framework/quantity_kinds.html#quantity-point-kinds]] {
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class quantity_point_kind<PointKind, Unit, Rep> [[../../framework/quantity_kinds.html#quantity-point-kinds]] {
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quantity_kind relative()
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}
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}
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Unit <.. Dimension
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Dimension <... Quantity
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Unit <... Quantity
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Dimension <... Kind
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Dimension <... PointOrigin
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PointOrigin <... PointKind
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Kind <... PointKind
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Unit <... QuantityPoint
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PointOrigin <... QuantityPoint
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quantity --* quantity_point
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Unit <... QuantityKind
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Kind <... QuantityKind
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quantity --* quantity_kind
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Unit <... QuantityPointKind
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PointKind <... QuantityPointKind
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quantity_kind --* quantity_point_kind
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@enduml
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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. Examples: ``second``, ``metre``, ``kilometre_per_hour``.
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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. Examples: ``si::dim_time``, ``si::dim_length``, ``si::dim_speed``.
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`Quantity` is a concrete amount of a unit for a specified dimension with a
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specific representation. Examples: ``quantity<si::dim_time, si::second, int>``,
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``si::length<si::metre, int>``, ``si::speed<si::kilometre_per_hour>``.
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`QuantityPoint` is an absolute `Quantity` with respect to an origin.
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Examples: timestamp (as opposed to duration), absolute temperature
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(as opposed to temperature difference).
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`QuantityKind` is a `Quantity` with more specific usage. Examples:
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distance (``horizonal_kind``) and height (``vertical_kind``) are different kinds
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of a length quantity.
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`QuantityPointKind` is an absolute `QuantityKind` with respect to an origin.
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Examples: altitude is a quantity point of ``vertical_kind`` (as opposed to
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height).
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