Textual types - The Rust Reference

# Textual types

The types `char` and `str` hold textual data.

A value of type `char` is a Unicode scalar value (i.e. a code point that is not a surrogate), represented as a 32-bit unsigned word in the 0x0000 to 0xD7FF or 0xE000 to 0x10FFFF range. It is immediate Undefined Behavior to create a `char` that falls outside this range. A `[char]` is effectively a UCS-4 / UTF-32 string of length 1.

A value of type `str` is represented the same way as `[u8]`, it is a slice of 8-bit unsigned bytes. However, the Rust standard library makes extra assumptions about `str`: methods working on `str` assume and ensure that the data in there is valid UTF-8. Calling a `str` method with a non-UTF-8 buffer can cause Undefined Behavior now or in the future.

Since `str` is a dynamically sized type, it can only be instantiated through a pointer type, such as `&str`.