Why3-Elpi: λProlog transformations for Why3

A library for embedding Elpi in Why3. The Why3-Elpi plugin allows users to write Why3 transformations as queries in the Elpi dialect of λProlog. The available API is visible in the w3lp.elpi file.

Quick start

Assumes opam is installed and a switch is active.

git clone git@github.com:manmatteo/why3-elpi.git
cd why3-elpi
opam install . --deps-only
dune build

Run an example transformation:

why3 prove tests/simple.mlw --extra-config why3extra.conf -D why3 -a "elpi_intro_implies"

Included Transforms & Examples

The examples/ directory contains reimplementations of common Why3 transformations in λProlog. Every file is then registered as a Why3 transformation in bin/why3_elpi_transformations.ml.

• elpi_intro_implies: Introduces top-level implications as local hypotheses.
• elpi_intros_full: Introduces top-level forall binders and implications.
• elpi_split_goal_and: Splits top-level goal conjunctions into multiple output tasks.
• elpi_drop_non_goal_props: Keeps goals and non-proposition declarations, drops lemmas/axioms.
• elpi_apply lemma [with t1, ..., tn]: Apply a lemma by giving its prsymbol and possibly a list of instantiation witnesses. Uses Elpi for unification.
• elpi_exists_term T: Instantiates the top-level existential with an explicit Why3 term T.
• elpi_tc: Compiles [@class] and [@instance] declarations into a witness-synthesis engine for existential goals.
• elpi_derive: Structurally synthesizes eq and ord witnesses based on helper combinators in scope.

How it works

The bridge between Why3 and Elpi is configured in lib/why3_elpi.ml. It provides builders to register the Why3 transformation wrappers into Why3's environment. When a user invokes a transformation like elpi_apply, the engine loads w3lp.elpi along with the specific code (e.g. examples/apply.elpi), and then calls the w3_run predicate to produce the new tasks.

# Local development: edit an example like examples/intro_implies.elpi and test the changes
dune exec -- why3 prove tests/simple.mlw --extra-config why3extra.conf -D why3 -a "elpi_intro_implies"