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Fix mp_eval_if_c example; add one for mp_eval_or

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Peter Dimov
2019-12-08 05:22:04 +02:00
parent 25cbde3f91
commit 3425d6bb00
1 changed files with 7 additions and 1 deletions
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8
doc/mp11/utility.adoc
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@@ -113,7 +113,7 @@ is to avoid evaluating `F<U...>` when the condition is `true` as it may not be v
.Using mp_eval_if_c to select the first pack element, or void
```
template<class... T> using first_or_void =
mp_eval_if_c<sizeof...(T) == 0, void, mp_apply, mp_first, mp_list<T...>>;
mp_eval_if_c<sizeof...(T) == 0, void, mp_first, mp_list<T...>>;
```
## mp_eval_if<C, T, F, U...>
@@ -175,6 +175,12 @@ Like `mp_valid`, but takes a quoted metafunction.
`mp_eval_or<T, F, U...>` is an alias for `F<U...>` when this expression is valid, for `T` otherwise.
.Using mp_eval_or to select the first pack element, or void
```
template<class... T> using first_or_void =
mp_eval_or<void, mp_first, mp_list<T...>>;
```
## mp_eval_or_q<T, Q, U...>
template<class T, class Q, class... U> using mp_eval_or_q =