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Implement closures.

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This commit is contained in:
Stephen Chung
2020-08-03 12:10:20 +08:00
parent 747c0345f2
commit 4079164bfd
24 changed files with 340 additions and 588 deletions
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22
doc/src/language/fn-closure.md
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@@ -15,7 +15,7 @@ is created.
Variables that are accessible during the time the [anonymous function] is created can be captured,
as long as they are not shadowed by local variables defined within the function's scope.
The values captured are the values of those variables at the time of the [anonymous function]'s creation.
The captured variables are automatically converted into reference-counted shared values.
New Parameters For Captured Variables
@@ -29,28 +29,32 @@ In actual implementation, this de-sugars to:
3. The variable is added to the parameters list of the anonymous function, at the front.
4. The current value of the variable is then [curried][currying] into the [function pointer] itself, essentially carrying that value and inserting it into future calls of the function.
4. The variable is then turned into a reference-counted shared value.
Automatic currying can be turned off via the [`no_capture`] feature.
5. The shared value is then [curried][currying] into the [function pointer] itself, essentially carrying a reference to that shared value and inserting it into future calls of the function.
Automatic currying can be turned off via the [`no_closure`] feature.
Examples
--------
```rust
let x = 40;
let x = 1;
let f = |y| x + y; // current value of variable 'x' is auto-curried
// the value 40 is curried into 'f'
let f = |y| x + y; // variable 'x' is auto-curried (captured) into 'f'
// 'x' is converted into a shared value
x = 1; // 'x' can be changed but the curried value is not
x = 40; // 'x' can be changed
f.call(2) == 42; // the value of 'x' is still 40
f.call(2) == 42; // the value of 'x' is 40 because 'x' is shared
// The above de-sugars into this:
fn anon$1001(x, y) { x + y } // parameter 'x' is inserted
let f = Fn("anon$1001").curry(x); // current value of 'x' is curried
make_shared(x); // convert 'x' into a shared value
let f = Fn("anon$1001").curry(x); // shared 'x' is curried
f.call(2) == 42;
```