A Simple Genetic Solver in Rust (Rustlang) -- see blog post https://handcraftsman.wordpress.com/2015/05/14/a-simple-genetic-solver-in-rust-rustlang/

Cargo.toml

[package]
name = "genetic"
version = "0.0.1"
authors = ["Clinton <[email protected]>"]

[dependencies]
rand = "*"
time = "*"

main.rs

extern crate time;
extern crate rand;

use rand::{thread_rng, sample, Rng};
use time::PreciseTime;

fn main() {
    let start = PreciseTime::now();
    let gene_set = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!.";
    let target = "Not all those who wander are lost.";
    let best = get_best(get_fitness, display, target, gene_set, target.len(), start);
    println!("{}", best);
    println!("Total time: {}", start.to(PreciseTime::now()));
}


fn get_best(get_fitness: fn(&String,&str) -> usize, display: fn(&String, &str, start: time::PreciseTime), target: &str, gene_set: &str, length: usize, start: time::PreciseTime) -> String {
	let mut best_parent = generate_parent(gene_set, length);
	let mut best_fitness = get_fitness(&best_parent, target);
	
	while best_fitness < length {
		let child = mutate_parent(&best_parent, gene_set);
		let fitness = get_fitness(&child, target);
		if fitness > best_fitness {
			best_fitness = fitness;
			best_parent = child;
			display(&best_parent, target, start);
		}
	}

	best_parent 
}

fn generate_parent(gene_set: &str, length: usize) -> String {
    let mut rng = thread_rng();
    let sample = sample(&mut rng, gene_set.chars(), length);
	sample.into_iter().collect()
}

fn mutate_parent(parent: &String, gene_set: &str) -> String {
    let mut rng = thread_rng();
	let gene_index = rng.gen::<usize>() % gene_set.len();
	let parent_index = rng.gen::<usize>() % parent.len();
	let mut candidate = String::with_capacity(parent.len());
    
	if parent_index > 0 {
		candidate.push_str(&parent[..parent_index]);
	}
	candidate.push_str(&gene_set[gene_index..(1+gene_index)]);
	if parent_index+1 < parent.len() {
		candidate.push_str(&parent[parent_index+1..]);
	}
	candidate
}

fn get_fitness(candidate: &String, target: &str) -> usize {
    let different_count = target.chars()
        .zip(candidate.chars())
        .filter(|&(a, b)| a != b)
        .count();
        
	target.len() - different_count
}

fn display(candidate: &String, target: &str, start: time::PreciseTime) {
    let now = PreciseTime::now();
    let elapsed = start.to(now);
    println!("{}\t{}\t{}", candidate, get_fitness(&candidate, target),elapsed);
}