boostorg/mp11
1
0
Fork 1
mirror of https://github.com/boostorg/mp11.git synced 2025-08-05 23:34:34 +02:00
Code Issues Packages Projects Releases Wiki Activity

Document mp_eval_if_not, mp_eval_or, mp_valid_q

Browse Source
This commit is contained in:
Peter Dimov
2019-02-15 03:09:07 +02:00
parent fc8bfcf601
commit d2b96e3a3f
3 changed files with 51 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
doc/mp11.adoc
View File

@@ -35,7 +35,7 @@ include::mp11/reference.adoc[]
This documentation is
* Copyright 2017 Peter Dimov
* Copyright 2017-2019 Peter Dimov
* Copyright 2017 Bjørn Reese
and is distributed under the http://www.boost.org/LICENSE_1_0.txt[Boost Software License, Version 1.0].

1
doc/mp11/changelog.adoc
View File

@@ -18,6 +18,7 @@ http://www.boost.org/LICENSE_1_0.txt
* Add `mp_not_fn`
* Add `mp_transform_first`, `mp_transform_second`, `mp_transform_third`
* Add `mp_filter`
* Add `mp_eval_if_not`, `mp_eval_or`, `mp_valid_q`
## Changes in 1.69.0

64
doc/mp11/utility.adoc
View File

@@ -1,5 +1,5 @@
////
Copyright 2017 Peter Dimov
Copyright 2017, 2019 Peter Dimov
Distributed under the Boost Software License, Version 1.0.
@@ -135,6 +135,53 @@ template<class L> using first_or_void = mp_eval_if<mp_empty<L>, void, mp_first,
Like `mp_eval_if`, but takes a quoted metafunction.
## mp_eval_if_not<C, T, F, U...>
template<class C, class T, template<class...> class F, class... U>
using mp_eval_if_not = mp_eval_if<mp_not<C>, T, F, U...>;
Same as `mp_eval_if`, but the condition is reversed.
## mp_eval_if_not_q<C, T, Q, U...>
template<class C, class T, class Q, class... U> using mp_eval_if_not_q =
mp_eval_if_not<C, T, Q::template fn, U...>;
Same as `mp_eval_if_not`, but takes a quoted metafunction.
## mp_valid<F, T...>
template<template<class...> class F, class... T> using mp_valid = /*...*/;
`mp_valid<F, T...>` is an alias for `mp_true` when `F<T...>` is a valid expression, for `mp_false` otherwise.
.Using mp_valid to write a metafunction that checks for the existence of a nested type
```
template<class T> using get_nested_type = typename T::type;
template<class T> struct has_nested_type: mp_valid<get_nested_type, T> {};
```
## mp_valid_q<Q, T...>
template<class Q, class... T> using mp_valid_q = mp_valid<Q::template fn, T...>;
Like `mp_valid`, but takes a quoted metafunction.
## mp_eval_or<T, F, U...>
template<class T, template<class...> class F, class... U> using mp_eval_or =
mp_eval_if_not<mp_valid<F, U...>, T, F, U...>;
`mp_eval_or<T, F, U...>` is an alias for `F<U...>` when this expression is valid, for `T` otherwise.
## mp_eval_or_q<T, Q, U...>
template<class T, class Q, class... U> using mp_eval_or_q =
mp_eval_or<T, Q::template fn, U...>;
Like `mp_eval_or`, but takes a quoted metafunction.
## mp_cond<C, T, R...>
template<class C, class T, class... R> using mp_cond = /*...*/;
@@ -156,19 +203,6 @@ template<int N> using unsigned_ = mp_cond<
>;
```
## mp_valid<F, T...>
template<template<class...> class F, class... T> using mp_valid = /*...*/;
`mp_valid<F, T...>` is an alias for `mp_true` when `F<T...>` is a valid expression, for `mp_false` otherwise.
.Using mp_valid to write a metafunction that checks for the existence of a nested type
```
template<class T> using get_nested_type = typename T::type;
template<class T> struct has_nested_type: mp_valid<get_nested_type, T> {};
```
## mp_defer<F, T...>
template<template<class...> class F, class... T> using mp_defer = /*...*/;
@@ -183,7 +217,7 @@ When `mp_valid<F, T...>` is `mp_true`, `mp_defer<F, T...>` is a struct with a ne
template<class... T> using fn = F<T...>;
};
`mp_quote<F>` transforms the template `F` into a type with a nested template `fn` such that `fn<T...>` returns `F<T...>`.
`mp_quote<F>` transforms the template `F` into a _quoted metafunction_, a type with a nested template `fn` such that `fn<T...>` returns `F<T...>`.
.Using mp_quote to make a list of metafunctions
```