T9

Predictive text in Rust

Motivation

I learned a neat trick from ag_dubs to come up with ports for your application. They used it during various RustBridge events.

The trick is to take a word that is relevant for your application and looking at the keypad of a phone.

By Sakurambo - Created using Adobe Illustrator CS2, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2048341

Lookup the corresponding number for each letter and that will be your port number.

Example

Let's take the word rust. Looking at the a keypad we find the following numbers

To the port number for your application would be 7878.

Hard work

Figuring out the correct keypad is hard work. Luckily that weher the t9 crate comes in. The following code could be used to figure the corresponding port for rust as well.

extern crate t9;

use std::env;
use t9::pad;

fn main() {
    let args: Vec<String> = env::args().collect();

    let port_name = &args[1];
    let port = pad::digits_for(port_name);
    println!("{}", port)
}

Calling it with cargo run --examples port -- rust returns 7878 as expected. port.rs can be found in the examples directory.

Reverse lookup

t9 also allows you to do a reverse lookup. I.e., what word was used for a given port number?

extern crate t9;

use std::env;
use std::fs::File;
use std::io::{self, BufRead, BufReader};
use t9::{pad, tree::Tree};

fn main() -> io::Result<()> {
    let mut tree = Tree::empty();
    let file = File::open("/usr/share/dict/american-english")?;
    let reader = BufReader::new(file);
    for word in reader.lines() {
        tree.add(word?);
    }

    let args: Vec<String> = env::args().collect();

    let port = &args[1];
    let digits = pad::digits_for(port);
    let words = tree.words_at(digits);
    for word in words {
        println!("{}", word)
    }
    Ok(())
}

Run with cargo run --release --example t9 -- 7878 returns the rust as expected. An more elaborate example, allowing you to specify the dictionary file, can be found in the examples directory.