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体验新版 GitCode,发现更多精彩内容 >>
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6ef8392b
编写于
10月 20, 2014
作者:
B
bors
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auto merge of #17453 : steveklabnik/rust/gh17340, r=alexcrichton
/cc @huonw
上级
b2e57736
f358407d
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with
120 addition
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22 deletion
+120
-22
src/doc/guide-strings.md
src/doc/guide-strings.md
+120
-22
未找到文件。
src/doc/guide-strings.md
浏览文件 @
6ef8392b
...
...
@@ -96,12 +96,11 @@ need, and it can make your lifetimes more complex.
## Generic functions
To write a function that's generic over types of strings, use
[
the `Str`
trait
](
http://doc.rust-lang.org/std/str/trait.Str.html
)
:
To write a function that's generic over types of strings, use
`&str`
.
```
{rust}
fn some_string_length
<T: Str>(x: T
) -> uint {
x.
as_slice().
len()
fn some_string_length
(x: &str
) -> uint {
x.len()
}
fn main() {
...
...
@@ -111,15 +110,12 @@ fn main() {
let s = "Hello, world".to_string();
println!("{}", some_string_length(s));
println!("{}", some_string_length(s
.as_slice()
));
}
```
Both of these lines will print
`12`
.
The only method that the
`Str`
trait has is
`as_slice()`
, which gives you
access to a
`&str`
value from the underlying string.
## Comparisons
To compare a String to a constant string, prefer
`as_slice()`
...
...
...
@@ -161,25 +157,93 @@ indexing is basically never what you want to do. The reason is that each
character can be a variable number of bytes. This means that you have to iterate
through the characters anyway, which is a O(n) operation.
To iterate over a string, use the
`graphemes()`
method on
`&str`
:
There's 3 basic levels of unicode (and its encodings):
-
code units, the underlying data type used to store everything
-
code points/unicode scalar values (char)
-
graphemes (visible characters)
Rust provides iterators for each of these situations:
-
`.bytes()`
will iterate over the underlying bytes
-
`.chars()`
will iterate over the code points
-
`.graphemes()`
will iterate over each grapheme
Usually, the
`graphemes()`
method on
`&str`
is what you want:
```
{rust}
let s = "
αἰθήρ
";
let s = "
u͔n͈̰̎i̙̮͚̦c͚̉o̼̩̰͗d͔̆̓ͥé
";
for l in s.graphemes(true) {
println!("{}", l);
}
```
This prints:
```
{notrust,ignore}
u͔
n͈̰̎
i̙̮͚̦
c͚̉
o̼̩̰͗
d͔̆̓ͥ
é
```
Note that
`l`
has the type
`&str`
here, since a single grapheme can consist of
multiple codepoints, so a
`char`
wouldn't be appropriate.
This will print out each character in turn, as you'd expect: first "α", then
"ἰ", etc. You can see that this is different than just the individual bytes.
Here's a version that prints out each byte:
This will print out each visible character in turn, as you'd expect: first "u͔", then
"n͈̰̎", etc. If you wanted each individual codepoint of each grapheme, you can use
`.chars()`
:
```
{rust}
let s = "αἰθήρ";
let s = "u͔n͈̰̎i̙̮͚̦c͚̉o̼̩̰͗d͔̆̓ͥé";
for l in s.chars() {
println!("{}", l);
}
```
This prints:
```
{notrust,ignore}
u
͔
n
̎
͈
̰
i
̙
̮
͚
̦
c
̉
͚
o
͗
̼
̩
̰
d
̆
̓
ͥ
͔
e
́
```
You can see how some of them are combining characters, and therefore the output
looks a bit odd.
If you want the individual byte representation of each codepoint, you can use
`.bytes()`
:
```
{rust}
let s = "u͔n͈̰̎i̙̮͚̦c͚̉o̼̩̰͗d͔̆̓ͥé";
for l in s.bytes() {
println!("{}", l);
...
...
@@ -189,16 +253,50 @@ for l in s.bytes() {
This will print:
```
{notrust,ignore}
206
177
225
188
117
205
148
110
204
142
205
136
204
176
206
184
206
105
204
153
204
174
207
205
154
204
166
99
204
137
205
154
111
205
151
204
188
204
169
204
176
100
204
134
205
131
205
165
205
148
101
204
129
```
...
...
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