dotcl

Common Lisp implementation on .NET. Lisp source is compiled to CIL (Common Intermediate Language) and runs on the .NET JIT — so the same Lisp image runs on Windows, macOS, and Linux across x86-64 and ARM64 without per-platform porting work.

Broadly conforms to the ANSI Common Lisp standard — verified against the ansi-test suite.

What dotcl is good for

Embedding Common Lisp in .NET applications. dotcl.runtime is a regular .NET library; you load it from any C# / F# / VB.NET project, evaluate Lisp code, and call back and forth.

is a regular .NET library; you load it from any C# / F# / VB.NET project, evaluate Lisp code, and call back and forth. Writing .NET code in Lisp. The dotnet: package gives direct access to .NET types: (dotnet:new "System.Text.StringBuilder") , (dotnet:invoke sb "Append" "x") , (dotnet:static "System.Math" "Sin" 1.0) . You can subclass .NET types from Lisp via dotnet:define-class — the compiler emits real .NET classes, so frameworks like MAUI, ASP.NET Core, and MonoGame just see them as ordinary subclasses.

The package gives direct access to .NET types: , , . You can subclass .NET types from Lisp via — the compiler emits real .NET classes, so frameworks like MAUI, ASP.NET Core, and MonoGame just see them as ordinary subclasses. Cross-platform CL with NuGet ecosystem access. Any NuGet package is reachable from Lisp; any Quicklisp library that doesn't rely on SBCL-only internals tends to work too (asdf, alexandria, etc. are routinely loaded).

Quick start

# One-time bootstrap: cross-compile dotcl's compiler with Roswell/SBCL. make cross-compile # Install as a `dotnet tool`-style global command. make install # REPL dotcl repl # Evaluate a form dotcl --eval " (format t \" hello, ~a~% \" (lisp-implementation-type)) " # Run a file dotcl --load my-program.lisp

After the first cross-compile, dotcl can self-host: DOTCL_LISP=dotcl make cross-compile rebuilds the compiler using dotcl itself.

Prerequisites

.NET SDK 10+ — see install table below

— see install table below Roswell (only for the initial cross-compile bootstrap — once dotcl is built it can rebuild itself)

Installing .NET SDK 10

OS Command macOS (Homebrew) brew install --cask dotnet-sdk Ubuntu 24.04+ sudo apt install dotnet-sdk-10.0 Debian add the Microsoft package repository, then apt install dotnet-sdk-10.0 — see official guide Windows (winget) winget install Microsoft.DotNet.SDK.10 Windows (Scoop) scoop install dotnet-sdk Cross-platform script dotnet-install.sh / dotnet-install.ps1 Other https://dotnet.microsoft.com/download

Samples

Working integrations in samples/ :

MauiLispDemo — a .NET MAUI app (Windows + Android) where Application / ContentPage / view model are all defined in Lisp via dotnet:define-class .

— a .NET MAUI app (Windows + Android) where / / view model are all defined in Lisp via . AspNetLispDemo — ASP.NET Core controller written in Lisp, with attribute routing.

— ASP.NET Core controller written in Lisp, with attribute routing. MonoGameLispDemo — Game subclass in Lisp; the Draw override runs on the MonoGame frame loop and animates the background colour.

— subclass in Lisp; the override runs on the MonoGame frame loop and animates the background colour. McpServerDemo — Model Context Protocol server exposing a Lisp REPL to MCP clients (Claude Desktop, etc.).

Each sample's README.md walks through the boot pattern.

Architecture

Compiler ( compiler/ , written in Lisp): transforms S-expressions into a flat list of CIL instructions (SIL).

( , written in Lisp): transforms S-expressions into a flat list of CIL instructions (SIL). Runtime ( runtime/ , written in C#): object representation, reader, CIL assembler ( PersistedAssemblyBuilder -based for .fasl output and Reflection.Emit for in-memory codegen), and the standard library functions that aren't expressible in pure Lisp.

( , written in C#): object representation, reader, CIL assembler ( -based for output and for in-memory codegen), and the standard library functions that aren't expressible in pure Lisp. Bootstrap is by cross-compile: a Roswell SBCL runs compiler/cil-compile.lisp to emit compiler/cil-out.sil , which the .NET runtime loads to bring up the Lisp environment. From that point dotcl can rebuild itself.

Architectural detail and design history are in DESIGN.md . Per-change rationale is recorded under docs/decisions/ .

Platform notes

Windows: see docs/windows.md for installation, encoding (UTF-8 stdin/stdout always), pathname conventions, and Windows-side .NET interop (Registry / WMI / WinForms / MAUI / COM).

License