ThinLisp is a Common Lisp implementation that translates a subset of Common Lisp to very efficient C code.

Note: ThinLisp is not actively developed. ECL is an active and supported Common Lisp to C compiler.

CLiCC is a similar system.

Authors: Jim Allard and Ben Hyde

Thinlisp is meant to allow deployment of CL-developed applications as efficient C-compiled code, and thus includes notable restrictions as compared to full CL semantics.

It is free software under an Apache 1.0 style license. This is the corresponding advertising clause:

3. All advertising materials mentioning features or use of this software must display the following acknowledgment: "This product includes software developed by the ThinLisp Group for use in the ThinLisp project ("

See (last updated 2001)

There is a slightly (2004) more up-to-date version available from

Tip: If the executables generated by ThinLisp are too large, try using strip. This shrinks the lecho demo binary from 555,893 to 119,020 bytes on a Red Hat Linux 6.2 system. If you compile it with make opt to use the C optimizer and then strip it, then the lecho binary size drops to 71,340.