diff options
Diffstat (limited to 'src/doc/book/listings/ch04-understanding-ownership/listing-04-08')
3 files changed, 36 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock new file mode 100644 index 000000000..2aa4918e5 --- /dev/null +++ b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "ownership" +version = "0.1.0" + diff --git a/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml new file mode 100644 index 000000000..e8847526d --- /dev/null +++ b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/Cargo.toml @@ -0,0 +1,6 @@ +[package] +name = "ownership" +version = "0.1.0" +edition = "2021" + +[dependencies] diff --git a/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/src/main.rs b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/src/main.rs new file mode 100644 index 000000000..b6182fe2b --- /dev/null +++ b/src/doc/book/listings/ch04-understanding-ownership/listing-04-08/src/main.rs @@ -0,0 +1,24 @@ +fn first_word(s: &String) -> usize { + let bytes = s.as_bytes(); + + for (i, &item) in bytes.iter().enumerate() { + if item == b' ' { + return i; + } + } + + s.len() +} + +// ANCHOR: here +fn main() { + let mut s = String::from("hello world"); + + let word = first_word(&s); // word will get the value 5 + + s.clear(); // this empties the String, making it equal to "" + + // word still has the value 5 here, but there's no more string that + // we could meaningfully use the value 5 with. word is now totally invalid! +} +// ANCHOR_END: here |