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copyediting: for loops

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Steve Klabnik 2015-04-10 12:21:14 -04:00
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src/doc/trpl/for-loops.md
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@ -1,10 +1,10 @@
% for Loops
The `for` loop is used to loop a particular number of times. Rust's `for` loops
work a bit differently than in other systems languages, however. Rust's `for`
loop doesn't look like this "C-style" `for` loop:
The `for` loop is used to loop a particular number of times. Rust’s `for` loops
work a bit differently than in other systems languages, however. Rust’s `for`
loop doesn’t look like this “C-style” `for` loop:
```{c}
```c
for (x = 0; x < 10; x++) {
printf( "%d\n", x );
}
@ -12,7 +12,7 @@ for (x = 0; x < 10; x++) {
Instead, it looks like this:
```{rust}
```rust
for x in 0..10 {
println!("{}", x); // x: i32
}
@ -20,25 +20,24 @@ for x in 0..10 {
In slightly more abstract terms,
```{ignore}
```ignore
for var in expression {
code
}
```
The expression is an iterator, which we will discuss in more depth later in the
guide. The iterator gives back a series of elements. Each element is one
iteration of the loop. That value is then bound to the name `var`, which is
valid for the loop body. Once the body is over, the next value is fetched from
the iterator, and we loop another time. When there are no more values, the
`for` loop is over.
The expression is an [iterator][iterator]. The iterator gives back a series of
elements. Each element is one iteration of the loop. That value is then bound
to the name `var`, which is valid for the loop body. Once the body is over, the
next value is fetched from the iterator, and we loop another time. When there
are no more values, the `for` loop is over.
[iterator]: iterators.html
In our example, `0..10` is an expression that takes a start and an end position,
and gives an iterator over those values. The upper bound is exclusive, though,
so our loop will print `0` through `9`, not `10`.
Rust does not have the "C-style" `for` loop on purpose. Manually controlling
Rust does not have the “C-style” `for` loop on purpose. Manually controlling
each element of the loop is complicated and error prone, even for experienced C
developers.
We'll talk more about `for` when we cover *iterators*, later in the Guide.