forked from boostorg/mp11
82 lines
3.2 KiB
Plaintext
82 lines
3.2 KiB
Plaintext
[/
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/ Copyright 2017 Peter Dimov
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/
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/ Distributed under the Boost Software License, Version 1.0. (See
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/ accompanying file LICENSE_1_0.txt or copy at
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/ http://www.boost.org/LICENSE_1_0.txt)
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/]
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[section:function Helper Metafunctions, `<boost/mp11/function.hpp>`]
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[section `mp_void<T...>`]
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template<class... T> using mp_void = void;
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Same as `std::void_t` from C++17.
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[endsect]
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[section `mp_and<T...>`]
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template<class... T> using mp_and = /*...*/;
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`mp_and<T...>` applies `mp_to_bool` to the types in `T...`, in order. If the result of an application is `mp_false`, `mp_and`
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returns `mp_false`. If the application causes a substitution failure, returns `mp_false`. If all results are `mp_true`,
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returns `mp_true`. `mp_and<>` is `mp_true`.
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using R1 = mp_and<mp_true, mp_true>; // mp_true
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using R2 = mp_and<mp_false, void>; // mp_false, void is not reached
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using R3 = mp_and<mp_false, mp_false>; // mp_false
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using R4 = mp_and<void, mp_true>; // mp_false (!)
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[endsect]
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[section `mp_all<T...>`]
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template<class... T> using mp_all = /*...*/;
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`mp_all<T...>` is `mp_true` if `mp_to_bool<U>` is `mp_true` for all types `U` in `T...`, `mp_false` otherwise. Same as
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`mp_and`, but does not perform short-circuit evaluation. `mp_and<mp_false, void>` is `mp_false`, but `mp_all<mp_false, void>`
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is an error because `void` does not have a nested `value`. The upside is that `mp_all` is potentially faster and does not
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mask substitution failures as `mp_and` does.
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using R1 = mp_and<mp_true, mp_true>; // mp_true
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using R2 = mp_and<mp_false, void>; // compile-time error
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using R3 = mp_and<mp_false, mp_false>; // mp_false
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using R4 = mp_and<void, mp_true>; // compile-time error
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[endsect]
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[section `mp_or<T...>`]
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template<class... T> using mp_or = /*...*/;
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`mp_or<T...>` applies `mp_to_bool` to the types in `T...`, in order. If the result of an application is `mp_true`, `mp_or`
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returns `mp_true`. If all results are `mp_false`, returns `mp_false`. `mp_or<>` is `mp_false`.
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using R1 = mp_or<mp_true, mp_false>; // mp_true
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using R2 = mp_or<mp_true, void>; // mp_true, void is not reached
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using R3 = mp_or<mp_false, mp_false>; // mp_false
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using R4 = mp_or<void, mp_true>; // compile-time error
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[endsect]
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[section `mp_any<T...>`]
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template<class... T> using mp_any = /*...*/;
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`mp_any<T...>` is `mp_true` if `mp_to_bool<U>` is `mp_true` for any type `U` in `T...`, `mp_false` otherwise. Same as
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`mp_or`, but does not perform short-circuit evaluation.
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using R1 = mp_any<mp_true, mp_false>; // mp_true
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using R2 = mp_any<mp_true, void>; // compile-time error
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using R3 = mp_any<mp_false, mp_false>; // mp_false
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using R4 = mp_any<void, mp_true>; // compile-time error
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[endsect]
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[section `mp_same<T...>`]
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template<class... T> using mp_same = /*...*/;
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`mp_same<T...>` is `mp_true` if all the types in `T...` are the same type, `mp_false` otherwise. `mp_same<>` is `mp_true`.
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[endsect]
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[section `mp_plus<T...>`]
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template<class... T> using mp_plus = /*...*/;
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`mp_plus<T...>` is an integral constant type with a value that is the sum of `U::value` for all types `U` in `T...`.
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`mp_plus<>` is `mp_int<0>`.
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[endsect]
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[endsect:function]
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