Macros within the same crate New method (since Rust 1.32, 2019-01-17) foo::bar!(); // works mod foo { macro_rules! bar { () => () } pub(crate) use bar; // <– the trick } foo::bar!(); // works With the pub use, the macro can be used and imported like any other item. And unlike the older method, … Read more
range_step_inclusive and range_step are long gone. As of Rust 1.28, Iterator::step_by is stable: fn main() { for x in (1..10).step_by(2) { println!(“{}”, x); } }
This is now touched on in the second edition of The Rust Programming Language. However, let’s dive in a bit in addition. Let us start with a simpler example. When is it appropriate to use a trait method? There are multiple ways to provide late binding: trait MyTrait { fn hello_word(&self) -> String; } Or: … Read more
Running cargo clean seems to fix the problem.
You can access the command line arguments by using the std::env::args or std::env::args_os functions. Both functions return an iterator over the arguments. The former iterates over Strings (that are easy to work with) but panics if one of the arguments is not valid unicode. The latter iterates over OsStrings and never panics. Note that the … Read more
Add a dependency section to your executable’s Cargo.toml and specify the path: [dependencies.my_lib] path = “../my_lib” or the equivalent alternate TOML: [dependencies] my_lib = { path = “../my_lib” } Check out the Cargo docs for specifying dependencies for more detail, like how to use a git repository instead of a local path.
I’ve found it useful to let the compiler guide me: fn to_words(text: &str) { // Note no return type text.split(‘ ‘) } Compiling gives: error[E0308]: mismatched types –> src/lib.rs:5:5 | 5 | text.split(‘ ‘) | ^^^^^^^^^^^^^^^ expected (), found struct `std::str::Split` | = note: expected type `()` found type `std::str::Split<‘_, char>` help: try adding a … Read more
It’s possible, but heap allocation is not allowed directly. Heap allocation is performed at runtime. Here are a few examples: static SOME_INT: i32 = 5; static SOME_STR: &’static str = “A static string”; static SOME_STRUCT: MyStruct = MyStruct { number: 10, string: “Some string”, }; static mut db: Option<sqlite::Connection> = None; fn main() { println!(“{}”, … Read more
The traits each represent more and more restrictive properties about closures/functions, indicated by the signatures of their call_… method, and particularly the type of self: FnOnce (self) are functions that can be called once FnMut (&mut self) are functions that can be called if they have &mut access to their environment Fn (&self) are functions … Read more