The glob operator (*) is a special character that can be used in Rust import statements to bring all public items defined in a path into scope. It is similar to the wildcard characters used in shell patterns.
To use the glob operator, simply specify the path to the module or crate you want to import, followed by the asterisk (*). For example, the following import statement brings all public items defined in the std::collections module into the current scope:
use std::collections::*;
This can be useful in some cases, such as when you need to use many items from a module or crate. However, it is important to be careful when using the glob operator, as it can make it more difficult to track what names are in scope and where they are defined.
The glob operator is often used in testing to bring all items under test into the tests module. This can be useful for writing comprehensive tests.
The glob operator is also sometimes used as part of the prelude pattern. The prelude is a set of modules and crates that are automatically imported into every Rust program. The standard library documentation provides a list of the modules and crates that are included in the prelude.
Here are some examples of how to use the glob operator:
// Import all public items from the std::collections module.
use std::collections::*;
// Import all public items from the tests module.
use tests::*;
// Import all public items from the prelude.
use prelude::*;
It is important to note that the glob operator only imports public items. Private items are not imported.
Also, keep in mind that the glob operator can make it more difficult to track what names are in scope and where they are defined. It is important to use it carefully and to document your code well.
