Tableau-based theorem prover for justification logic.

An implementation of a decision procedure for classical propositional logic and justification logic.

judge

judge is a modular implementation of a decision procedure for classical and justification logics, through a tableau-based theorem prover.

Installation

judge can be installed through Cabal:

cabal sandbox init
cabal install judge

A recommended alternative is to use Stack, for which you will need to clone the repository and do:

stack install

Usage

judge expects a logical system to be defined in the YAML or JSON format. This file will specify the type of proof system and the logical family (although at the moment, only the respective values tableau and justification are recognised). It also provides the rules of inference. See the logic directory for example specifications.

If no target formula(s) are provided via -g, formulas are read off the standard input. If no output file is provided via -o, the result is written to the standard output. By default, the format is plain text; add -f LaTeX to obtain LaTeX code instead.

For example, the following will construct proofs for theorems of the logic LP (with c:(A→B→A) ∊ CS), and produces a PDF file to visualise them:

judge LP \
    -a "c:(A->B->A)" \
    -f LaTeX \
     < formulas.txt \
     | pdflatex

Contributing

Notable missing features are detailed on the issue tracker.

Contributions that extend judge to different logical families (modal, first order...) or proof systems (sequent, natural deduction...) are welcomed.