# Applications and libraries/Theorem provers

### From HaskellWiki

## Theorem provers

Tools for formal reasoning, written in Haskell.

- Agda
- Agda is a system for incrementally developing proofs and programs. Agda is also a functional language with Dependent types. This language is very similar to cayenne and agda is intended to be a (almost) full implementation of it in the future.

- Djinn
- Djinn generates Haskell code from a type declaration, using a decision procedure from intuitionistic propositional calculus.

- Paradox
- Paradox processes first-order logic problems and tries to find finite-domain models for them.

- Dumatel
- Dumatel is a prover based on many-sorted term rewriting (TRW) and equational reasoning

- Camila
- Camila is a system for software development using formal methods. Other materials on formal methods can be found also on the analysis and design page.

- Epigram
- Epigram is a prototype dependently typed functional programming language, equipped with an interactive editing and typechecking environment. High-level Epigram source code elaborates into a dependent type theory based on Zhaohui Luo's UTT. Programming with evidence lies at the heart of Epigram's design.

- Cayenne
- Cayenne is a functional language with a powerful dependent type system. The basic types are functions, products, and sums. Functions and products use dependent types to gain additional power. As with Epigram, a dependently typed language may be used to encode strong proofs in the type system.

- Yarrow
- Yarrow is a proof-assistant for Pure Type Systems (PTSs) with several extensions. In Yarrow you can experiment with various pure type systems, representing different logics and programming languages.

- Proof General Kit
- The Proof General Kit designs and implements a component-based framework for interactive theorem proving. The central middleware of the toolkit is implemented in Haskell. The project is the sucessor of the highly successful Emacs-based Proof General interface.

- Expander2
- Expander2 is a flexible multi-purpose workbench for rewriting, verification, constraint solving, flow graph analysis and related procedures that build up proofs or computation sequences. Moreover, tailor-made interpreters display terms as 2D structures ranging from trees and rooted graphs to tables, fractals and other turtle-system-generated pictures.

- DEMO
- Model checking for dynamic epistemic logic. DEMO is a tool for modelling change in epistemic logic (the logic of knowledge). Among other things, DEMO allows modeling epistemic updates, graphical display of update results, graphical display of action models, formula evaluation in epistemic models, translation of dynamic epistemic formulas to PDL (propositional dynamic logic) formulas. More materials and other Haskell resources on dynamic epistemic modelling (and more generally on logic and linguistics) can be found on Jan van Eijck's page.