rexxlings

Interactive exercises for learning REXX, a classic scripting language.

Inspired by rustlings, rexxlings guides you through REXX programming concepts via small exercises that you fix and complete in your editor.

Home Code Repository is at git.navicore.tech

PRs and issues welcome at codeberg.org mirror

Prerequisites

• Rust toolchain (to build rexxlings): rustup.rs
• rexx interpreter (patch-rexx): must be in your PATH

Getting Started

# Build
cargo build --release

# Run in the project directory (watch mode starts automatically)
cargo run

# Or install globally
cargo install --path .
rexxlings

Watch mode monitors your exercise files and automatically re-checks when you save.

Development

Build, test, and lint go through just. The justfile is the single source of truth — CI calls just ci and nothing else, so local checks cannot drift from CI.

just ci          # fmt-check + clippy (warnings=errors) + tests + release build
just fmt         # apply rustfmt
just test        # run tests only
just install     # install rexxlings into ~/.cargo/bin
just stats       # LOC + largest files + module tree (needs scc + cargo-modules)

The toolchain version is pinned in rust-toolchain.toml and matched by the toolchain: input of every CI workflow under .forgejo/workflows/. CI runs on Forgejo Actions (Linux) for every pull request to main.

How It Works

1. Rexxlings presents exercises one at a time, starting with the basics
2. Open the exercise file in your editor and follow the instructions in the comment header
3. Fix the code, then delete the /* I AM NOT DONE */ marker
4. Rexxlings detects the change and advances to the next exercise

Commands

Command	Description
rexxlings	Start watch mode (default)
rexxlings list	Show all exercises with status
rexxlings hint	Show hint for current exercise
rexxlings verify	Check all exercises
rexxlings next	Skip to the next exercise
rexxlings reset [name]	Reset an exercise
rexxlings init [dir]	Extract exercises to a new directory

Chapter Filter

rexxlings watch --chapter 07
rexxlings list --chapter 03

Curriculum

135 exercises across 23 chapters:

Part 1: Foundations

• 00-intro — Hello world, comments, string literals
• 01-variables — SAY, assignment, uninitialized variables, concatenation
• 02-arithmetic — Operators, precedence, comparison, logical operators
• 03-strings-intro — LENGTH, SUBSTR, LEFT, RIGHT, COPIES, REVERSE, POS

Part 2: Control Flow

• 04-conditionals — IF/THEN/ELSE, nested IF, NOP, compound conditions, strict comparison
• 05-select — SELECT/WHEN/END, OTHERWISE, DO blocks, nested SELECT, FizzBuzz
• 06-do-loops — DO/END, counted loops, FOREVER, WHILE, UNTIL, LEAVE, ITERATE

Part 3: String Processing

• 07-string-bifs — STRIP, TRANSLATE, SPACE, OVERLAY, INSERT, DELSTR, CHANGESTR, COMPARE
• 08-word-bifs — WORDS, WORD, WORDINDEX, WORDLENGTH, SUBWORD, WORDPOS, DELWORD
• 09-parse — Word splitting, literal patterns, positional patterns, dot placeholder, PARSE VALUE

Part 4: Subroutines & Data

• 10-subroutines — CALL/RETURN, PROCEDURE, EXPOSE, ARG, function syntax, recursion
• 11-stem-variables — Compound variables, defaults, string keys, multi-dimensional, patterns

Part 5: Numeric Features

• 12-numeric-bifs — ABS, SIGN, MAX, MIN, TRUNC, FORMAT, RANDOM
• 13-conversions — D2X, X2D, C2D, D2C, C2X, X2C, B2X, X2B, DATATYPE

Part 6: Advanced Features

• 14-advanced-parse — Multi-template, PARSE UPPER, variable patterns, PARSE SOURCE, CSV parsing
• 15-advanced-do — Computed bounds, DO WHILE+TO combos, loop idioms
• 16-interpret — Dynamic code execution with INTERPRET
• 17-signal — SIGNAL for jumps and error trapping (SYNTAX, NOVALUE)
• 18-numeric-precision — NUMERIC DIGITS, large numbers, FUZZ, FORM, 100!

Part 7: I/O & System

• 19-queues — PUSH/PULL (LIFO), QUEUE (FIFO), QUEUED()
• 20-address — ADDRESS SYSTEM, return codes, shell integration
• 21-date-time — DATE(), TIME(), date formats, XRANGE

Part 8: Practical Challenges

• 22-practical — Word frequency, Caesar cipher, palindrome, Roman numerals, bubble sort, RPN calculator, text formatter, and more

License

MIT