Substring method for string types.

This crate provides a substring method on Rust string types. The method takes a start and end character index and returns a string slice of the characters within that range.

The method is provided via the Substring trait which is implemented on the &str primitive.

Usage

To use this crate, simply bring the Substring trait into scope and call the substring method on your string types.

```rust use substring::Substring;

assert_eq!("hello, world!".substring(7, 12), "world"); ```

Performance

As Rust strings are UTF-8 encoded, the algorithm for finding a character substring has temporal complexity O(n), where n is the byte length of the string. This is due to characters not being of predictible byte lengths.

Caution

The indexing of substrings is based on Unicode Scalar Value. As such, substrings may not always match your intuition:

```rust use substring::Substring;

asserteq!("y̆".substring(0, 1), "y"); // As opposed to "y̆". asserteq!("y̆".substring(1, 2), "\u{0306}") // The diacritical mark counts as its own character. ```

The above example occurs because "y̆" is technically made up of two UTF-8 scalar values.