Twelf is the current version of a succession of implementations of the logical framework LF. Previous systems include Elf (which provided type reconstruction and the operational semantics reimplemented in Twelf) and MLF (which implemented module-level constructs loosely based on the signatures and functors of ML still missing from Twelf).
Twelf should be understood as research software. This means comments, suggestions, and bug reports are extremely welcome, but there are no guarantees regarding response times. The same remark applies to these notes which constitute the only documentation on the present Twelf implementation.
For current information including download instructions, publications, and mailing list, see the Twelf home page at http://www.cs.cmu.edu/~twelf/. This User's Guide is published as
Frank Pfenning and Carsten Schuermann Twelf User's Guide Technical Report CMU-CS-98-173, Department of Computer Science, Carnegie Mellon University, November 1998.
Below we state the typographic conventions in this manual.
File names for examples given in this guide are relative to the main
directory of the Twelf installation. For example
`examples/guide/nd.elf' may be found in
`/usr/local/twelf/examples/guide/nd.elf' if Twelf was installed into the `/usr/local/' directory.
The current version 1.3 from September 13, 2000 incorporates the following major changes from Twelf 1.2 from August 27, 1998.
%prove) and ignore those with
%establish, which is otherwise equivalent. In unsafe mode,
%assertcan be used to claim theorems. However, at present no longer generates proof terms.
%abbrev) which, unlike definition, do not need to be strict.
%name) now allow an optional second argument for naming of parameters.
Assuming you are running on a Unix system with SML of New Jersey already
installed (see section 13 Installation) you can build Twelf as follows. Here
`%' is assumed to be the shell prompt. You may need to edit the
file `Makefile' to give the proper location for
% gunzip twelf-1-3.tar.gz % tar -xf twelf-1-3.tar % cd twelf % make % bin/twelf-server Twelf 1.3, Sep 13 2000 %% OK %%
You can now load the examples used in this guide and pose an example
query as shown below. The prompt from the Twelf top-level is `?-'.
To drop from the Twelf top-level to the ML top-level, type C-c
(CTRL c). To exit the Twelf server you may issue the
quit command or type C-d (CTRL c).
Config.read examples/guide/sources.cfg Config.load top ?- of (lam [x] x) T. Solving... T = arrow T1 T1. More? y No more solutions ?- C-c interrupt %% OK %% quit %
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