tmp/tmp95j3clv7/{from.md → to.md}
RENAMED
|
@@ -0,0 +1,27 @@
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1 |
+
### General <a id="exec.queryable.general">[[exec.queryable.general]]</a>
|
| 2 |
+
|
| 3 |
+
A *queryable object* is a read-only collection of key/value pair where
|
| 4 |
+
each key is a customization point object known as a *query object*. A
|
| 5 |
+
*query* is an invocation of a query object with a queryable object as
|
| 6 |
+
its first argument and a (possibly empty) set of additional arguments. A
|
| 7 |
+
query imposes syntactic and semantic requirements on its invocations.
|
| 8 |
+
|
| 9 |
+
Let `q` be a query object, let `args` be a (possibly empty) pack of
|
| 10 |
+
subexpressions, let `env` be a subexpression that refers to a queryable
|
| 11 |
+
object `o` of type `O`, and let `cenv` be a subexpression referring to
|
| 12 |
+
`o` such that `decltype((cenv))` is `const O&`. The expression
|
| 13 |
+
`q(env, args...)` is equal to [[concepts.equality]] the expression
|
| 14 |
+
`q(cenv, args...)`.
|
| 15 |
+
|
| 16 |
+
The type of a query expression cannot be `void`.
|
| 17 |
+
|
| 18 |
+
The expression `q(env, args...)` is equality-preserving
|
| 19 |
+
[[concepts.equality]] and does not modify the query object or the
|
| 20 |
+
arguments.
|
| 21 |
+
|
| 22 |
+
If the expression `env.query(q, args...)` is well-formed, then it is
|
| 23 |
+
expression-equivalent to `q(env, args...)`.
|
| 24 |
+
|
| 25 |
+
Unless otherwise specified, the result of a query is valid as long as
|
| 26 |
+
the queryable object is valid.
|
| 27 |
+
|