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refactor: "expression templates" renamed to "symbolic expressions"
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Mateusz Pusz
@ -270,7 +270,7 @@
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[`derived dimension`](#derived-dimension){ #derived-dimension }
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: - A [dimension](#dimension) of a [derived quantity](#derived-quantity).
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- Implemented as an expression template being the result of the
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- Implemented as an symbolic expression being the result of the
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[dimension equation](#dimension-equation) on [base dimensions](#base-dimension).
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[`dimension equation`](#dimension-equation){ #dimension-equation }
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@ -159,7 +159,7 @@ The above prints:
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Some users could expect to see `42 kWh` or `42 kW h` in the output. It is not the case and for
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a very good reason. As stated in
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[Simplifying the resulting expression templates](../users_guide/framework_basics/interface_introduction.md#simplifying-the-resulting-expression-templates),
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[Simplifying the resulting symbolic expressions](../users_guide/framework_basics/interface_introduction.md#simplifying-the-resulting-symbolic-expressions),
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to be able to reason about and simplify units, the library needs to order them in an appropriate
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order.
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@ -35,7 +35,7 @@ To achieve this goal, several techniques are applied:
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compile-times and the readability of error messages when compared to the traditional template
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metaprogramming with [SFINAE](https://en.cppreference.com/w/cpp/language/sfinae),
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- [usage of strong types for framework entities](../users_guide/framework_basics/interface_introduction.md#strong-types-instead-of-aliases) (instead of type aliases),
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- [usage of expression templates](../users_guide/framework_basics/interface_introduction.md#expression-templates) to improve the readability of generated types,
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- [usage of symbolic expressions](../users_guide/framework_basics/interface_introduction.md#symbolic-expressions) to improve the readability of generated types,
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- limiting the number of template arguments to the bare minimum.
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!!! important "Important: It is all about errors"
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@ -141,7 +141,7 @@ ratio of `1` and does not output any textual symbol.
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!!! important "Important: `one` is an identity"
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A unit `one` is special in the entire type system of units as it is considered to be
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[an identity operand in the unit expression templates](interface_introduction.md#identities).
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[an identity operand in the unit symbolic expressions](interface_introduction.md#identities).
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This means that, for example:
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```cpp
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@ -24,7 +24,7 @@ behind this is that:
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Also, to prevent possible issues in compile-time logic, all of the library's entities must be
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marked `final`. This prevents the users to derive own strong types from them, which would
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prevent expression template simplification of equivalent entities.
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prevent symbolic expressions simplification of equivalent entities.
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## Strong types instead of aliases
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@ -103,14 +103,14 @@ inline constexpr struct joule final : named_unit<"J", newton * metre> {} joule;
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```
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## Expression templates
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## Symbolic expressions
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The previous chapter provided a rationale for not having predefined types for derived entities.
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In many libraries, such an approach results in long and unreadable compilation errors, as
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framework-generated types are typically far from being easy to read and understand.
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The **mp-units** library greatly improves the user experience by extensively using
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expression templates. Such expressions are used consistently throughout the entire library
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symbolic expressions. Such expressions are used consistently throughout the entire library
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to describe the results of:
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- [dimension equation](../../appendix/glossary.md#dimension-equation) - the result is put into
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@ -169,7 +169,7 @@ constexpr auto my_unit = one / second;
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constexpr auto my_unit = inverse(second);
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```
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Both cases will result in the same expression template being generated and put into the wrapper
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Both cases will result in the same symbolic expression being generated and put into the wrapper
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class template.
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@ -195,10 +195,10 @@ its unique representation in the library:
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| `sqrt({identity})` or `pow<1, 2>({identity})` | `{identity}` |
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### Simplifying the resulting expression templates
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### Simplifying the resulting symbolic expressions
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To limit the length and improve the readability of generated types, there are many rules to simplify
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the resulting expression template.
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the resulting symbolic expression.
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1. **Ordering**
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@ -246,7 +246,7 @@ the resulting expression template.
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Also, to prevent possible issues in compile-time logic, all of the library's entities must be
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marked `final`. This prevents the users to derive own strong types from them, which would
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prevent expression template simplification of equivalent entities.
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prevent symbolic expression simplification of equivalent entities.
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4. **Repacking**
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@ -96,7 +96,7 @@ All of the above quantities are equivalent and mean exactly the same.
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The above code example may give the impression that the order of components in a derived
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unit is determined by the multiplication order. This is not the case. As stated in
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[Simplifying the resulting expression templates](interface_introduction.md#simplifying-the-resulting-expression-templates),
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[Simplifying the resulting symbolic expressions](interface_introduction.md#simplifying-the-resulting-symbolic-expressions),
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to be able to reason about and simplify units, the library needs to order them in an
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appropriate order. This will affect the order of components in a resulting type and
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text output.
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@ -55,7 +55,6 @@ add_mp_units_module(
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include/mp-units/framework/customization_points.h
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include/mp-units/framework/dimension.h
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include/mp-units/framework/dimension_concepts.h
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include/mp-units/framework/expression_template.h
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include/mp-units/framework/quantity.h
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include/mp-units/framework/quantity_cast.h
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include/mp-units/framework/quantity_concepts.h
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@ -67,6 +66,7 @@ add_mp_units_module(
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include/mp-units/framework/reference_concepts.h
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include/mp-units/framework/representation_concepts.h
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include/mp-units/framework/symbol_text.h
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include/mp-units/framework/symbolic_expression.h
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include/mp-units/framework/system_reference.h
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include/mp-units/framework/unit.h
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include/mp-units/framework/unit_concepts.h
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@ -22,8 +22,8 @@
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#pragma once
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/quantity_spec.h>
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#include <mp-units/framework/symbolic_expression.h>
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#include <mp-units/framework/unit_concepts.h>
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namespace mp_units {
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@ -32,8 +32,8 @@
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#include <mp-units/ext/prime.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/customization_points.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#include <mp-units/framework/unit_magnitude_concepts.h>
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#include <mp-units/framework/unit_symbol_formatting.h>
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@ -28,7 +28,6 @@
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#include <mp-units/framework/customization_points.h>
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#include <mp-units/framework/dimension.h>
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#include <mp-units/framework/dimension_concepts.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/quantity.h>
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#include <mp-units/framework/quantity_cast.h>
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#include <mp-units/framework/quantity_concepts.h>
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@ -39,6 +38,7 @@
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#include <mp-units/framework/reference.h>
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#include <mp-units/framework/representation_concepts.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#include <mp-units/framework/system_reference.h>
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#include <mp-units/framework/unit.h>
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#include <mp-units/framework/unit_concepts.h>
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@ -31,8 +31,8 @@
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#include <mp-units/ext/inplace_vector.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/dimension_concepts.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#ifndef MP_UNITS_IN_MODULE_INTERFACE
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#include <mp-units/ext/contracts.h>
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@ -122,7 +122,7 @@ struct base_dimension : detail::dimension_interface {
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* Derived dimension is an expression of the dependence of a quantity on the base quantities of a system of quantities
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* as a product of powers of factors corresponding to the base quantities, omitting any numerical factors.
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*
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* Instead of using a raw list of exponents this library decided to use expression template syntax to make types
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* Instead of using a raw list of exponents this library decided to use symbolic expression syntax to make types
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* more digestable for the user. The positive exponents are ordered first and all negative exponents are put as a list
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* into the `per<...>` class template. If a power of exponent is different than `1` the dimension type is enclosed in
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* `power<Dim, Num, Den>` class template. Otherwise, it is just put directly in the list without any wrapper. There
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@ -25,8 +25,8 @@
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// IWYU pragma: private, include <mp-units/framework.h>
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#include <mp-units/bits/module_macros.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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namespace mp_units {
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@ -32,11 +32,11 @@
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#include <mp-units/ext/type_name.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/dimension.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/quantity_concepts.h>
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#include <mp-units/framework/quantity_spec_concepts.h>
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#include <mp-units/framework/reference_concepts.h>
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#include <mp-units/framework/representation_concepts.h>
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#include <mp-units/framework/symbolic_expression.h>
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#ifndef MP_UNITS_IN_MODULE_INTERFACE
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#ifdef MP_UNITS_IMPORT_STD
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@ -439,7 +439,7 @@ struct derived_quantity_spec_impl :
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* Its dimension is an expression of the dependence of a quantity on the base quantities of a system of
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* quantities as a product of powers of factors corresponding to the base quantities, omitting any numerical factors.
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*
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* Instead of using a raw list of exponents this library decided to use expression template syntax to make types
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* Instead of using a raw list of exponents this library decided to use symbolic expression syntax to make types
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* more digestable for the user both for quantity specification and its dimension. The positive exponents are ordered
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* first and all negative exponents are put as a list into the `per<...>` class template. If a power of exponent
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* is different than `1` the quantity type is enclosed in `power<Q, Num, Den>` class template. Otherwise, it is
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@ -26,7 +26,7 @@
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#include <mp-units/bits/hacks.h>
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#include <mp-units/bits/module_macros.h>
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#include <mp-units/framework/dimension_concepts.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/symbolic_expression.h>
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namespace mp_units {
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@ -33,10 +33,10 @@
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#include <mp-units/ext/inplace_vector.h>
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#include <mp-units/ext/type_name.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/quantity_point_concepts.h>
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#include <mp-units/framework/quantity_spec_concepts.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#include <mp-units/framework/unit_concepts.h>
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#include <mp-units/framework/unit_magnitude.h>
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#include <mp-units/framework/unit_symbol_formatting.h>
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@ -24,9 +24,9 @@
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// IWYU pragma: private, include <mp-units/framework.h>
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#include <mp-units/bits/module_macros.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/quantity_spec_concepts.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#include <mp-units/framework/unit_magnitude.h>
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namespace mp_units {
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@ -25,8 +25,8 @@
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// IWYU pragma: private, include <mp-units/framework.h>
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#include <mp-units/bits/module_macros.h>
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#include <mp-units/ext/type_traits.h>
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#include <mp-units/framework/expression_template.h>
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#include <mp-units/framework/symbol_text.h>
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#include <mp-units/framework/symbolic_expression.h>
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#ifndef MP_UNITS_IN_MODULE_INTERFACE
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#ifdef MP_UNITS_IMPORT_STD
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