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// ANCHOR: here
fn first_word ( s : & str ) -> & str {
// ANCHOR_END: here
let bytes = s . as_bytes ( ) ;
for ( i , & item ) in bytes . iter ( ) . enumerate ( ) {
if item = = b' ' {
return & s [ 0 .. i ] ;
}
}
& s [ .. ]
}
// ANCHOR: usage
fn main ( ) {
let my_string = String ::from ( "hello world" ) ;
// `first_word` 适用于 `String`（的 slice） ，
let word = first_word ( & my_string [ 0 .. 6 ] ) ;
let word = first_word ( & my_string [ .. ] ) ;
// `first_word` 也适用于 `String` 的引用，
// 这等价于整个 `String` 的 slice
let word = first_word ( & my_string ) ;
let my_string_literal = "hello world" ;
// `first_word` 适用于字符串字面值，部分或全部
let word = first_word ( & my_string_literal [ 0 .. 6 ] ) ;
let word = first_word ( & my_string_literal [ .. ] ) ;
// 因为字符串字面值已经 **是** 字符串 slice 了，
// 这也是适用的，无需 slice 语法！
let word = first_word ( my_string_literal ) ;
}
// ANCHOR_END: usage
