substring 1.4.0

A substring method for string types.
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# substring


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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");
```

Note that the indexing of substrings is based on
[*Unicode Scalar Value*](http://www.unicode.org/glossary/#unicode_scalar_value). As such,
substrings may not always match your intuition:

```rust
use substring::Substring;

assert_eq!("ã".substring(0, 1), "a");  // As opposed to "ã".
assert_eq!("ã".substring(1, 2), "\u{0303}")
```

The above example occurs because "ã" is technically made up of two UTF-8 scalar values: the letter
"a" and a combining tilde.


## 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.

## Minimum Supported Rust Version

This crate is guaranteed to compile on stable `rustc 1.0.0` and up. Use in a `no_std` Rust environment
requires stable `rustc 1.6.0` and up.