A Rust implementation of https://flownet.com/ron/papers/lisp-java/instructions.html. As recently popularised by @renatoathaydes.

Mainly exploring the performance gains possible through avoiding recursion and keeping memory allocations fairly tightly controlled.

Seems to compare favourably to Renato's fast-rust-no-bigint-buffer-stdout branch:

Test setup

$ curl -s 'https://raw.githubusercontent.com/dwyl/english-words/master/words.txt' | tail -100000 > words.txt

 $ wc -l words.txt
 100000 words.txt

 $ cat phones_1_len_29.txt
 91760687651618841752033181652

Poorly controlled benchmark results

fast-rust-no-bigint-buffer-stdout version (00:01:44)

 $ time ./phone_encoder words.txt phones_1_len_29.txt | wc -l
 201009600
 ./phone_encoder words.txt phones_1_len_29.txt  101.97s user 2.53s system 99% cpu 1:44.51 total

This version (00:00:19)

 $ time ./rust-laatj words.txt phones_1_len_29.txt | wc -l
 201009600
 ./rust-laatj words.txt phones_1_len_29.txt  16.85s user 2.57s system 99% cpu 19.426 total