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.
• 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.
• 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
• Roswell (only for the initial cross-compile bootstrap — once dotcl is built it can rebuild itself)

Installing .NET SDK 10

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.
• AspNetLispDemo — 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.
• 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).
• 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.
• 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

MIT. See LICENSE.