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Add the loop_break_value feature to the reference #53

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Add the loop_break_value feature to the reference #53

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8d7e097
Fix wrong quotes in the Expressions chapter
pietroalbini May 12, 2017
f8dfbdc
Add documentation for loop_break_value
pietroalbini May 12, 2017
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15 changes: 14 additions & 1 deletion src/expressions.md
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Expand Up @@ -564,7 +564,7 @@ Significantly, lambda expressions _capture their environment_, which regular
[function definitions](items.html#functions) do not. The exact type of capture
depends on the [function type](types.html#function-types) inferred for the
lambda expression. In the simplest and least-expensive form (analogous to a
```|| { }``` expression), the lambda expression captures its environment by
`|| { }` expression), the lambda expression captures its environment by
reference, effectively borrowing pointers to all outer variables mentioned
inside the function. Alternately, the compiler may infer that a lambda
expression should copy or move values (depending on their type) from the
Expand Down Expand Up @@ -600,6 +600,11 @@ within this loop may exit out of this loop or return control to its head.
See [break expressions](#break-expressions) and [continue
expressions](#continue-expressions).

A `loop` expression is [diverging](items.html#diverging-functions), and doesn't
return anything. However, when it contains a [break
expression](#break-expressions), it returns the value attached to the `break`
that caused the loop to stop.

## `break` expressions

A `break` expression has an optional _label_. If the label is absent, then
Expand All @@ -608,6 +613,14 @@ enclosing it. It is only permitted in the body of a loop. If the label is
present, then `break 'foo` terminates the loop with label `'foo`, which need not
be the innermost label enclosing the `break` expression, but must enclose it.

When the `break` expression is enclosed in a `loop` it has an optional return
value attached which will be returned by the loop ended by the
expression. When it's not provided it defaults to `()`.

If both a label and a return value are present in the expression, the label
must be placed before the return value. For example `break 'label 42` breaks
the loop labelled `'label`, returning `42` from it.

## `continue` expressions

A `continue` expression has an optional _label_. If the label is absent, then
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