An interactive tutor for learning LL(1) and SLR(1) parsing.

SyntaxTutor helps compiler students understand how LL(1) and SLR(1) parsers are built. The student works through each algorithm one question at a time: FIRST and FOLLOW sets, prediction symbols, LR(0) items, closures, transitions and, finally, the parsing table. Every answer is checked on the spot, and a wrong answer leads to smaller questions that rebuild the reasoning step by step, so the student learns why a result is what it is.

Note

Project status. SyntaxTutor 2.0 is the final feature release. The project is considered complete, and no further development is planned.

Contents

• Features
• Getting started
• How it works
• Screenshots
• Documentation
• Building from source
• Project structure
• Background
• License

Features

• Step-by-step tutors for LL(1) and SLR(1), with immediate feedback on every answer.
• Pedagogical branching: mistakes open smaller questions instead of revealing the result.
• Your own grammars: a grammar editor with live validation, or generated grammars at three difficulty levels.
• Exam mode: no feedback during the exercise, a 0–10 grade at the end and a question-by-question review.
• LR(0) automaton drawn progressively as the student computes states and transitions.
• Guided table modes that walk through the LL(1) and SLR(1) tables one cell at a time.
• PDF export of the conversation, sets, automaton states, parsing tables and exam reports.
• Quick references for the theory of both algorithms.
• Spanish and English interface, adjustable text size and gamified progress.

Getting started

Download the build for your system from the latest release. No installation or Internet connection is needed.

System	Download	Requirements
Windows	SyntaxTutor-<version>-windows-x64.zip	Windows 10 or 11, 64-bit
macOS	SyntaxTutor-<version>-macos-arm64.zip	Apple Silicon (M1 or later)
Linux	SyntaxTutor-<version>-x86_64.AppImage	Ubuntu 22.04, Debian 12 or newer

• Windows: unzip and run SyntaxTutor.exe.
• macOS: unzip, move SyntaxTutor.app to Applications and open it.
• Linux: chmod +x SyntaxTutor-<version>-x86_64.AppImage and run it. It uses X11, or XWayland on Wayland desktops; start it with QT_QPA_PLATFORM=wayland to run natively on Wayland.

Warning

The Windows and macOS builds are not digitally signed, so the system may warn you the first time you open them. The user manual explains how to open them anyway. Only do so with files downloaded from this repository.

Once the application is open, the Tutorial button on the home screen gives a short tour of the interface and the first exercises.

How it works

LL(1). The tutor asks for the size of the predictive table and then, rule by rule, for the prediction symbols. A wrong answer is broken down into the FIRST set of the right-hand side and the FOLLOW set of the left-hand side before the question is asked again. The exercise ends with the LL(1) table, where wrong cells are highlighted and a guided mode is available.

SLR(1). The tutor starts from the closure of the initial item and builds the LR(0) collection state by state: number of items, symbols after the dot and every transition δ(I, X). It then covers the table dimensions, states with complete items, LR(0) conflicts resolved with FOLLOW sets and reduce-only states, and ends with the SLR(1) parsing table.

Screenshots

Home. Choose a tutor, the difficulty, your own grammar or exam mode.	Grammar editor. Live validation; only LL(1) or SLR(1) grammars are accepted.
LL(1) tutor. A wrong answer leads to questions about FIRST and FOLLOW.	LL(1) table. Wrong cells are highlighted after each submission.
SLR(1) tutor. Building the LR(0) collection, transition by transition.	LR(0) automaton. It grows as each state is computed.
SLR(1) table. sN, rN, acc and goto entries.	Guided mode. One cell at a time, with a hint for each.
LL(1) guided mode. The same help for the predictive table.	Exam report. The grade and a review of every answer, exportable to PDF.

Documentation

• User manual: English · Español
• Developer documentation (Doxygen): online · PDF
• Changes between versions: CHANGELOG

The developer documentation covers every class and function, with dependency and inheritance graphs. To regenerate it, install Doxygen and Graphviz and run doxygen from the repository root; the output goes to docs/.

Building from source

Requirements:

• Qt 6, including qmake6 and the Qt SVG module
• A C++20 compiler: GCC 11 or newer, a recent Clang, or MSVC 2022
• GoogleTest, only for the backend tests

With GNU make, the repository's GNUmakefile builds out of tree:

make app     # the application, in build/app
make check   # backend and GUI tests

make check-core and make check-ui run each suite on its own; the same tests run in CI on every push and pull request. To use qmake directly, pass -f Makefile, because GNU make would otherwise pick up the GNUmakefile:

qmake6
make -f Makefile

Project structure

Path	Contents
src/backend/	Grammar model and parsing engine: FIRST/FOLLOW, LL(1) table, LR(0) items and the SLR(1) table, in plain C++20 with no Qt dependency.
src/gui/	Main window, the LL(1) and SLR(1) tutors with their question flows, table dialogs, guided modes, exam report and PDF export.
src/widgets/	Reusable widgets and helpers: chat input, grammar view, LR(0) automaton view, tutorial overlay, typography and settings.
src/app/	Application entry point.
tests/	GUI tests with fixed grammar fixtures; the backend tests live in src/backend/tests.cpp.
resources/	Icon, logo, fonts and the application style sheet.
translations/	Spanish and English translations.
manual/, docs/	User and developer manuals, and the generated Doxygen output.

Background

SyntaxTutor 1.x was the Final Degree Project "Interactive Tutorial About Syntax Analyzers" (2025). Version 2 is a later extension and redesign, developed independently of that project: it adds custom grammars, exam mode, the LR(0) automaton, guided table modes and a new interface. See the CHANGELOG for the full list.

License

SyntaxTutor is free software, released under the GNU General Public License v3.0. It is built with Qt 6, also available under the GPLv3, and bundles the JetBrains Mono font under the SIL Open Font License.

Created by José R.. If you use SyntaxTutor in a course or build on it, a mention of the project is appreciated.