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| -rw-r--r-- | src/doc/guide.md | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/src/doc/guide.md b/src/doc/guide.md index 8493a30a16e..9a1a42478d3 100644 --- a/src/doc/guide.md +++ b/src/doc/guide.md @@ -4601,20 +4601,24 @@ returns `true` or `false`. The new iterator `filter()` produces only the elements that that closure returns `true` for: ```{rust} -for i in range(1i, 100i).filter(|x| x % 2 == 0) { +for i in range(1i, 100i).filter(|&x| x % 2 == 0) { println!("{}", i); } ``` This will print all of the even numbers between one and a hundred. +(Note that because `filter` doesn't consume the elements that are +being iterated over, it is passed a reference to each element, and +thus the filter predicate uses the `&x` pattern to extract the integer +itself.) You can chain all three things together: start with an iterator, adapt it a few times, and then consume the result. Check it out: ```{rust} range(1i, 1000i) - .filter(|x| x % 2 == 0) - .filter(|x| x % 3 == 0) + .filter(|&x| x % 2 == 0) + .filter(|&x| x % 3 == 0) .take(5) .collect::<Vec<int>>(); ``` |