PreScheme aka Pre-Scheme
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PreScheme (also spelled Pre-Scheme) is a statically typed dialect of Scheme that gives the programmer the efficiency and low-level machine access of C while retaining many of the desirable features of Scheme.

The PreScheme compiler makes use of type inference, partial evaluation and Scheme and Lisp compiler technology to compile the problematic features of Scheme, such as closures, into C code without significant run-time overhead. Use of such features in PreScheme programs is restricted to those cases that can be compiled into efficient code.

Type reconstruction is done using a modified Hindley/Milner algorithm that allows overloaded user-defined functions.

All top-level forms in PreScheme programs are evaluated at compile time, which gives the user additional control over the compiler's partial evaluation of a program.

PreScheme has been implemented and used to write a byte-code interpeter and associated support code for a complete Scheme implementation.



Scheme 48


No known public release.


SPS is a Pre-Scheme to (GNU) C compiler written in Pre-Scheme.

Written in 1999.


Pre-Scheme for Guile

A port of Pre-Scheme from Scheme 48 to Guile.

Started in 2022.


Research papers

From the MITRE Corporation:

  • A Verified Compiler for Pure PreScheme (1991)
  • The VLISP PreScheme Front End (1992)
  • A Verified Run-Time Structure for Pure PreScheme (1992)
  • The Revised VLISP PreScheme Front End (1993)
  • The VLISP Verified PreScheme Compiler (1995)
  • A Verified Compiler for Multithreaded PreScheme (1996)

From Kelsey:

  • Pre-Scheme: A Scheme Dialect for Systems Programming (1997)