Crate newstr

Simple macros for declaring String-base new types.

This crate provides simple macros that generate String based new types. The two primary macros implement the validity rules for the new type by either 1) providing a predicate that is used by the is_valid associated function, or 2) providing a function to parse and return a string which is then called by FromStr::from_str.

Both of these methods produce a new type, with the following:

1. An associated predicate function is_valid that returns true if the string provided would be a valid value for the type.
2. This type derives implementations of Clone, Debug, PartialEq, PartialOrd, Eq, Ord, and Hash.
3. An implementation of Display for T that simply returns the inner value.
4. An implementation of From<T> for String.
5. An implementation of Deref for T with the target type str.
6. An implementation of FromStr.

Example

The following example constructs a new string type that implements an Identifier value. This value must be ASCII, alphanumeric, the '_' character and must not be empty.

```rust use std::fmt::{Display, Formatter}; use std::str::FromStr; use std::ops::Deref;

fn isidentifiervalue(s: &str) -> bool { !s.isempty() && s.chars().all(|c| c.isasciialphanumeric() || c == '') }

isvalidnewstring!(Identifier, isidentifiervalue);

assert!(!Identifier::isvalid("")); assert!(!Identifier::isvalid("hi!")); assert!(!Identifier::isvalid("hello world")); assert!(!Identifier::isvalid("9.99"));

asserteq!( Identifier::fromstr("hi").unwrap().tostring(), String::from("hi") ); asserteq!( Identifier::fromstr("helloworld").unwrap().tostring(), String::from("helloworld") ); ```