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What Is Common Larceny?

Common Larceny is a variant of Larceny, a simple and efficient run-time system for Scheme. It is built to run on the ECMA Common Language Infrastructure (CLI). In Common Larceny, Scheme code is compiled to Common Intermediate Language, and is then assembled into bytecode for execution by native just-in-time (JIT) compilers.

When used in conjunction with Microsoft's .NET Framework, which includes an implementation of the CLI, the Common Language Runtime, Common Larceny provides an interface to the .NET Framework class library, allowing developers to take full advantage of dozens of predefined classes designed to facilitate application development.

Who Developed Common Larceny?

Common Larceny was initially developed between 2002 and 2004 by Ryan Culpepper, Joe Marshall, Dale Vaillancourt, and others under the direction of Will Clinger and Matthias Felleisen at Northeastern University. Felix Klock, Jesse Tov, and Chris Burns have contributed to the latest development of Common Larceny.

Obtaining Common Larceny

The easiest way to start using Common Larceny is to download a binary distribution bundle. Each bundle contains a Common Larceny executable file, and the libraries required by the executable. If you'd like to build from source, you can do that, too. However, first you must ensure that your system meets certain requirements.

System Requirements

Currently, this software is distributed for Windows on Intel x86 machines, Microsoft .NET Framework 2.0.

Common Larceny may work on other platforms (e.g. Mac OS X with the Mono Framework 1.1) but we do not yet provide support for those systems.

Common Language Infrastructure

Common Larceny requires the Common Language Infrastructure. It is known to work with the Microsoft .NET Framework implementation. In the past, some releases of Common Larceny have worked with Mono also, but we have not tested the current release with Mono. It is also conceivable that Common Larceny might work with DotGNU Portable.NET or Microsoft Shared Source CLI (Rotor), but it hasn't been tried.

When using the Microsoft .NET Framework implementation of the CLI, you only need the .NET redistributable package, but the .NET SDK contains a much richer set of utilities and documentation.

Environment Variables

Common Larceny requires you to have the environment variable LARCENY_ROOT defined as the root directory of your larceny distribution, e.g. C:\Larceny\.

For more information on managing environment variables in Windows XP, see Microsoft Knowledge Base Article 310519.

Binary Distribution

Choose one of these binary distribution bundles:

The CommonLarceny.exe executable is a console program. When it is started, it will print a number of diagnostic lines and then enter a read-eval-print loop.

Note: The distributed bundles also include the Larceny.exe executable. This is not a standalone application so no attempt should be made to run the file on its own.

Source Distribution

If you would like to build Common Larceny from source, download the source distribution (Gzipped TAR File). Once you have downloaded the source distribution, the instructions below should enable you to build Common Larceny yourself.

Building from Source


To build Common Larceny from source, you will need a working version of regular Larceny. (You might be able to use Petite Chez or MzScheme instead, but they have not been tested recently and are not recommended.)

You will also need to have a couple of executable programs available in your path. You may need to edit src\Rts\DotNet\makefile to use appropriate programs on your system.

Once you have ensured the above requirements are met, start your host Scheme system, and change to the root of the Larceny distribution, if necessary. The current-directory procedure should do the trick. Then, load the configuration file for Common Larceny: (load "src/Build/dotnet.sch")

Next, you need to inform the build tool of the specifics of the host environment. Invoke larceny-setup with three or four arguments:

> (larceny-setup <host-scheme> <os> <endianness> <codegen-options>)


For example, to build under Larceny on a Windows machine, using Microsoft's C/C++ Compiler, you would use:

> (larceny-setup "Larceny" 'win32 'little 'use-cl)

After setting up the environment for building Larceny, evaluate the following:

> (build-config-files)
> (load-compiler)

The first procedure builds the config files (Rts\*.cfg), and the second loads the Twobit compiler. You can't load the compiler until after you have run larceny-setup and build-config-files.

The .NET Heap

The next step involves building the .NET heap. After loading the compiler in the previous step, simply evaluate:

> (make-dotnet-heap)

This procedure loads the Scheme files needed to build the .NET heap and compiles and assembles their contained code to MSIL code in three stages. First it compiles Scheme code to MacScheme code (.lap files), then assembles the MacScheme code into s-expressions representing MSIL code, (.lop files), and finally dumps these s-expressions as raw MSIL code (.code-il files).

Evaluating make-dotnet-heap produces a file in the root of the Larceny distribution, dotnet.heap.exe. This is the executable file that you will run to load Common Larceny. In bundled distributions, we rename this to CommonLarceny.exe.

The Runtime System

Lastly, you will need to build the runtime system:

> (build-runtime-system)

This procedure will create Scheme.dll in the src\Rts\DotNet directory. The Scheme.dll library contains the classes that make up the Common Larceny runtime. Copy Scheme.dll into the root directory of the Larceny Distribution.

You should now have a working copy of Common Larceny in your LARCENY_ROOT directory. Rename dotnet.heap.exe to CommonLarceny.exe (not necessary but suggested) and run it to enter the interactive read-eval-print loop.


Running the CommonLarceny.exe executable alone loads Common Larceny as an interpreted Scheme system. It is also possible to load Common Larceny so that it compiles Scheme code upon load. This creates slightly longer load times, but can improve execution times by quite a bit.

To build the fast-loading (.fasl) and .exe files used to invoke the CompileOnLoad version of Common Larceny, first build the heap and the runtime-system as described above. Then run:

> (build-larceny)

This will create new files in the root of your Common Larceny distribution, namely Larceny.exe and Larceny.fasl. These files are required to run the CompileOnLoad version of Common Larceny.

To use the CompileOnLoad version of Common Larceny, invoke the runtime with:

CommonLarceny Larceny.fasl.

Compiling the R6RS and ERR5RS Runtime Libraries

If you want to use Common Larceny to run R6RS or ERR5RS programs, then you will need to compile the R6RS runtime system and the R6RS standard libraries.

To do so, first remove any and all .fasl and .slfasl files from the lib/R6RS directory and its subdirectories. Then:

CommonLarceny Larceny.fasl
> (require 'r6rsmode)
> (larceny:compile-r6rs-runtime)

This will take a very long time, and will print numerous messages to the screen about files not found.

Using Common Larceny

Common Larceny can be run in any of three modes:

R5RS Mode

To run Common Larceny in its default R5RS mode, just run the CommonLarceny.exe like this:


To compile files as they are loaded, add Larceny.fasl to the command line, like this:

CommonLarceny Larceny.fasl


To run Common Larceny in ERR5RS mode, add the —err5rs command-line option, like this:

CommonLarceny Larceny.fasl --err5rs

R6RS Mode

To run R6RS programs in Common Larceny, you will need to specify the —r6rs and —program command-line options, and may also need to use the —path option.

Suppose, for example, that you want to run an R6RS program named myprogram.sps that may use some of the standard R6RS libraries, some of the ERR5RS/R6RS libraries provided by Common Larceny, and some of the ERR5RS/R6RS SRFI libraries provided by Common Larceny, but does not define or use any other libraries. Then you can run the program like this:

CommonLarceny Larceny.fasl --r6rs --program myprogram.sps

If the program defines its own libraries, or uses libraries other than those provided by Common Larceny, then you will need to tell Common Larceny where those libraries reside by using the —path command-line option or the LARCENY_LIBPATH environment variable, both of which are documented in the Larceny User Manual, which is online at

Compiling Code to Run within Common Larceny

The same compiler that is used to compile files as they are loaded can also be used to compile files ahead of time, which makes them load faster.

Compiling a file with Common Larceny is now done the same way as in native Larceny. See the Larceny User Manual, which is online at

Suppose, for example, that you want to compile two files that contain R5RS code, even.sch and odd.sch. You can compile them as follows:

CommonLarceny Larceny.fasl
> (compile-file "even.sch")
> (compile-file "odd.sch")
> (exit)

After the files have been compiled, you can load them into a new session of Common Larceny by listing the names of the compiled files on the command line, like this:

CommonLarceny Larceny.fasl even.fasl odd.fasl

You can also use the load procedure to load the compiled files into a session of Common Larceny that is already running:

CommonLarceny Larceny.fasl
> (load "even.fasl")
> (load "odd.fasl")

Once compiled, a compiled file cannot be moved because its absolute path name is wired into the compiled file. This restriction may be removed in some future version of Common Larceny.