STELF (System for Totality in the Edinburgh Logical Framework)

This is the STELF project, a port of the Twelf system to OCaml, and subsequents developments thereof.

Twelf Port

The Twelf port, which is completed, involved translating between SML to OCaml, and also the creation of a temporary basis library. If you are interested in looking at the process, see shibboleth

From Twelf to STELF

The STELF project, which is still in devolopment, involves a number of changes to the original Twelf codebase, designed to do the following:

• Imporove the syntax
  • Remove unnecassary special syntax (Parsing done, printing not started)
  • Simplify the language
  • Make the codebase trivial to parse for editor integration
  • Overhaul the parser (Nearly done)
• Increase performance (WIP)
• Make the codebase more flexible, particular in regards to custom frontends
  • Changed the design of the concrete syntax tree to not depend on the actual concrete syntax, but instead be view based (CST is done, but integration is not)
  • Make the codebase more modular, and break up larger modules / libraries into smaller ones (WIP)
  • Make documentation consistent (WIP)
  • Testing
• Create a cleaner frontend
  • Internally, the frontend is exposed at one point (Mostly done)
  • Output should be given and then dealt with, not done internally (Not started)
  • Create a nicer REPL (Done)
  • Create a nicer CLI (Done)

Heavy inspiration was taken from the following sources:

• Rocq (interlopability)
• Z3 theorem prover (language design)
• Metamath (minimalism)

Documentation

Documentation is very incomplete, but the following resources are available:

• The dev docs are not yet available, but running source hacking.sh BROWSER where BROWSER is your browser should (propably (on Linux (maybe ))) open the dev docs (hopefully). Dev docs are not done
• The wiki contains some documentation, but is also incomplete.
• The STELF book, which is intended to be both a manual and reference, is located in the book directory. It is also incomplete, and as a little experiment is written in Typst.
• Some other useful links include:
  • Original Twelf repo and website
  • The Shibboleth transpiler
  • A certain paper describing canonical LF
  • Building, which is hopefully up to date

If you couldn't tell, this project is a tad large. If I miss something, please reach out.

Original README

Copyright (C) 1997-2011, Frank Pfenning and Carsten Schuermann

Authors:

Frank Pfenning
Carsten Schuermann

With contributions by:

Brigitte Pientka
Roberto Virga
Kevin Watkins
Jason Reed

STELF

Copyright (C) 2026, Asher Frost