capture.rs
==============
[](https://travis-ci.org/Kimundi/lazy-static.rs)
A macro for adding explicit capture clauses to a (closure-) expression.
Using this macro, it becomes possible to be explicit about what
variables a closure captures, and by which capture mode it does so.
# Syntax
```ignore
capture!($([move IDENT,]
[ref IDENT,]
[IDENT IDENT,])*
in EXPR)
```
# Semantic
The macro will expand to nested block expressions with a `let` binding per capture clause:
- The `move x` clause rebinds a name by itself, which is effectively a no-op.
- The `ref x` clause rebinds a name by a shared reference to it.
- The `ref mut x` clause rebinds a name by a mutable reference to it.
- The `IDENT x` clause rebinds a name to the result of calling `.IDENT()` method on it.
This can for example be used to capture by clone, which would look like this: `clone x`.
These bindings will be in scope for the final `EXPR` expression, which will usually be a
by-value capturing closure.
# Current limitations and future changes
- The macro syntax makes it somewhat verbose. A future version of this package
might make use of expression-attributes instead to become more lightweight.
- The macro might become more specialized to always produce a by-value capturing closure,
rather than allowing arbitrary expressions.
# Example
Using the macro:
```rust
#![feature(phase)]
#![feature(unboxed_closures)]
#[phase(plugin)]
extern crate capture;
fn main() {
let (x, y, z) = (1u32, 2u32, 3u32);
let g = capture!(move x, ref y, clone z in move |:| x + *y + z);
assert_eq!(g(), 6);
}
```
```