v4script lets a Qt application run programs written in fifteen
languages - from QBasic and Turbo Pascal classics to Go, C++, Java, C# and
WebAssembly - inside the JavaScript engine that every Qt Qml installation
already has. No compilers, no external processes, no native interpreters:
one static library, a few lines of C++, and your users can script your
application in the language they like.
v4script::Runtime runtime;
runtime.setOutput([](v4script::Stream, const QString& text) { std::cout << text.toStdString(); });
runtime.run("basic", "FOR i = 1 TO 3: PRINT i * i;: NEXT"); // 1 4 9
runtime.run("pascal", "WriteLn('Pi = ', Pi:0:5);"); // Pi = 3.14159
runtime.run("go", "fmt.Println(strings.Repeat(\"Go\", 3))"); // GoGoGo
Why v4script
- 🧩 Fifteen languages, one engine. Every language runs in the same
QJSEngine as JavaScript, shares its global object and can call
JavaScript - and the other way round.
- 🔌 Your API in every language. Give programs a
QObject and its
methods become a Go package, a C or C++ header, a Java or C# class, a
Pascal unit, Prolog predicates and Scheme procedures - with names and types in
the conventions of each language.
- 🎯 Faithful behavior. The translated languages are checked against
real implementations: Pascal prints numbers exactly as Free Pascal does,
BASIC follows QBasic down to
PRINT USING and RND, C has its own
memory with real pointers, the C++ library gives the numbers of
libstdc++'s <random> and the order of its hash tables, C# formats
numbers and orders dictionaries as .NET does, WebAssembly passes the
specification tests.
- 🛡️ Safe to embed. Programs see only what the application gives them:
output, standard input, module files, a canvas. A watchdog stops runaway
code, deep recursion is an error, not a crash.
- 🎨 Graphics included. QBasic
SCREEN 13 and Pascal Graph draw on a
canvas - into a QImage or a Qt Quick Canvas.
- 📦 Pick what you need. Embed all languages (about 14 MB of scripts,
7.4 MB minified) or just the few your application uses.
Supported languages
| Language | Version | What runs | Implementation |
|---|
| Python | 3 | Python 3 (the subset of Skulpt) | Skulpt ae5f462 |
| Lua | 5.3 | Lua 5.3 | fengari 0.1.5 |
| Prolog | ISO | ISO Prolog | Tau Prolog 0.3.4 |
| Perl | 5 | Perl 5 (the subset of Perlito5) | Perlito5 9.028 |
| PHP | 7 | PHP 7 (the subset of Uniter) | Uniter (phpruntime 9.3.0) |
| Go | 1.22 | Go with goroutines, channels, generics and a subset of the standard library | v4script 0.1.4 |
| C | C17 | C17 with its own linear memory and a subset of the C library | v4script 0.1.4 |
| C++ | C++17 | C++17 over the memory of C: classes, templates, exceptions, lambdas and an STL that behaves as libstdc++ | v4script 0.1.4 |
| Java | 21 | Java 21 with records, pattern matching, threads, streams and a JDK subset | v4script 0.1.4 |
| C# | 12 | C# 12 with generics, LINQ, records, patterns, async/await, threads and a .NET 8 subset | v4script 0.1.4 |
| Forth | 2012 | Forth 2012, compatible with gforth | v4script 0.1.4 |
| BASIC | QBasic 4.5 | QBasic / QuickBASIC 4.5 with graphics | v4script 0.1.4 |
| Pascal | FPC 3.2.2 | Free Pascal 3.2.2 (objfpc): classes, exceptions, SysUtils, Math, StrUtils, Classes, Crt, Graph | v4script 0.1.4 |
| WebAssembly | 2.0 | the WAT text format, .wast scripts, WASI | v4script 0.1.4 |
| Scheme | R7RS | R7RS-small, SRFI 1, 13, 18, 69, full continuations | v4script 0.1.4 |
Languages marked v4script are translated into JavaScript by v4script's
own translator; the others run in third-party interpreters written in
JavaScript. Versions are available to the application too:
v4script::languages() and v4script::version().
Coming next
The translator grows one language at a time, in this order:
Kotlin, Rust, Swift, Dart, Scala, F#, Haskell, Erlang, Fortran,
COBOL, Nim, Zig, x86 assemblers (NASM, FASM, TASM) and ASMX, Verilog,
MASM, Ada, Common Lisp, the NES (ca65) and Z80 (sjasmplus) assemblers,
CoffeeScript, the .NET IL assembler. See TODO for the plan and
the known gaps.
Try it online
The playground runs all fifteen
languages in the browser with the same scripts: pick an example - BASIC
games and graphics, Pascal Graph, goroutines in Go, records in Java,
LINQ in C#,
call/cc in Scheme - or write your own program; it stays in your browser.
How it works and how it differs from the Qt engine:
playground.
Documentation
- ▶️ Playground - the languages in the browser, built
for GitHub Pages with
node tools/build-site.mjs
- 🚀 Getting started - build, try the examples
and the
v4run command-line runner
- 📚 Languages - what each language supports
and how programs use the application's API
- 🔧 Embedding - CMake integration, the C++ API,
host modules, graphics
- ⚙️ Internals - how the translator and the
interpreters work on V4
- 🧪 Testing and
development
All documentation: docs/.
Building
cmake -S . -B build -DCMAKE_PREFIX_PATH=<path to Qt>/<kit>
cmake --build build --parallel
ctest --test-dir build --output-on-failure
Requires Qt 6.4 or later (developed with 6.4.1), CMake 3.19 and a C++17
compiler. To use it in your project, add it as a subdirectory and link
V4Script::V4Script - see embedding.
This is the beginning of the README. Read the rest at the original. Read the full README ↗
