tmp/tmpibo3ebcc/{from.md → to.md}
RENAMED
|
@@ -0,0 +1,21 @@
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1 |
+
#### Class template `is_placeholder` <a id="func.bind.isplace">[[func.bind.isplace]]</a>
|
| 2 |
+
|
| 3 |
+
``` cpp
|
| 4 |
+
namespace std {
|
| 5 |
+
template<class T> struct is_placeholder; // see below
|
| 6 |
+
}
|
| 7 |
+
```
|
| 8 |
+
|
| 9 |
+
`is_placeholder` can be used to detect the standard placeholders `_1`,
|
| 10 |
+
`_2`, and so on. `bind` uses `is_placeholder` to detect placeholders.
|
| 11 |
+
|
| 12 |
+
Instantiations of the `is_placeholder` template shall meet the
|
| 13 |
+
UnaryTypeTrait requirements ([[meta.rqmts]]). The implementation shall
|
| 14 |
+
provide a definition that has the BaseCharacteristic of
|
| 15 |
+
`integral_constant<int, J>` if `T` is the type of
|
| 16 |
+
`std::placeholders::_J`, otherwise it shall have a BaseCharacteristic of
|
| 17 |
+
`integral_constant<int, 0>`. A program may specialize this template for
|
| 18 |
+
a user-defined type `T` to have a BaseCharacteristic of
|
| 19 |
+
`integral_constant<int, N>` with `N > 0` to indicate that `T` should be
|
| 20 |
+
treated as a placeholder type.
|
| 21 |
+
|