loglings

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   "Logic programs, slightly broken."

Interactive exercises for learning Prolog, powered by patch-prolog.

Inspired by rustlings and seqlings.

Prerequisites

You need patch-prolog installed and on your PATH. See the patch-prolog README for setup.

Quick start

cargo install loglings           # or: cargo install --path . from a local clone
loglings init                    # creates ./my-loglings with all exercises
cd my-loglings
loglings                         # starts watch mode

The exercises, hints, and reference solutions all live inside the loglings binary — init just extracts them into a directory you choose. You never need to clone this repo to use the tool.

In watch mode, loglings re-checks the current exercise as you save the file and advances when it passes.

To reset a single exercise back to its starting state:

loglings reset 01-fact

How it works

1. loglings shows the current exercise
2. Open the .pl file in your editor
3. Read the comment, fix or complete the code
4. Delete the % I AM NOT DONE marker when you think it's done
5. loglings re-checks on save and advances to the next exercise on success

Commands

Command	Description
loglings init [path]	Create a fresh workspace (default ./my-loglings)
loglings update	Refresh untouched exercises from a newer loglings (your in-progress work is preserved)
loglings update --dry-run	Show what update would do, without writing
loglings update --force <name>	Force-replace a specific exercise even if you've touched it
loglings	Watch mode (default, when run inside a workspace)
loglings list	Show all exercises with status
loglings verify	Check every exercise once
loglings hint	Print a hint for the current exercise
loglings hint <name>	Hint for a specific exercise
loglings next	Skip to the next exercise
loglings reset	Reset the current exercise to original
loglings reset <name>	Reset a specific exercise

Curriculum (starting slice)

Section	Topics
00-intro	Facts, queries, multiple solutions, rules, lists

More sections will be added as the curriculum grows. The engine is still gaining features; expect new sections to follow new engine capabilities.

Prolog basics

Prolog is declarative logic programming. You write facts and rules; you ask questions; the engine searches for answers.

% A fact: parent(tom, bob) means "tom is a parent of bob"
parent(tom, bob).
parent(tom, liz).
parent(bob, ann).

% A rule: grandparent(X, Z) if X is a parent of some Y and Y is a parent of Z
grandparent(X, Z) :- parent(X, Y), parent(Y, Z).

Ask a question:

?- grandparent(tom, X).
X = ann.

Reporting issues

If an exercise feels unfair, the hint is wrong, or you've discovered an engine gap (loglings refuses to accept your obviously-correct answer because the engine can't parse it), please open an issue at:

• Curriculum/runner issues: loglings issues
• Engine bugs: patch-prolog issues

License

MIT