F* vs Why3
F*
fstar-lang.orgWhy3
why3.orgSide by side
| Figure | F* | Why3 |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | — | Yes |
| Windows | Yes | Yes |
| macOS | Yes | — |
| Linux | Yes | Yes |
| API | — | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Formal Verification Tools | 8.0 (#11) | 8.0 (#12) |
| Development | F* is open source on GitHub and is under active development by Microsoft Research, Inria, and the community. | Why3 is developed by the Inria Toccata team, a joint research team of Inria Saclay-Île-de-France, Université Paris-Saclay, and CNRS. |
| Installation | The project offers binaries for Windows, Linux, and Mac OS X, and installation through OPAM, Docker, Nix, or source builds. | Why3 can be installed via Opam, run from a Docker image, or compiled from source. |
| License | F* is distributed under the Apache 2.0 license. | TryWhy3 is distributed under the GNU Lesser General Public License version 2.1 with a special linking exception. |
| Purpose | F* is a general-purpose proof-oriented programming language for purely functional and effectful programming. | Why3 is a platform for deductive program verification that uses WhyML and external theorem provers to discharge verification conditions. |
Plans
In their own words
Why3
Why3 is a platform for deductive program verification. It uses WhyML to express programs and specifications, then works with external automated or interactive theorem provers to discharge verification conditions. WhyML supports preconditions, postconditions, assertions, and loop invariants, alongside logical theories and data structures such as arrays, queues, and hash tables. External provers need to be installed and configured separately. Why3 can be extended with support for new provers and used as a software library through its OCaml API. WhyML programs can be extracted automatically into correct-by-construction OCaml programs, and WhyML is also used as an intermediate language for verification of C, Java, Rust, and Ada. TryWhy3 provides a JavaScript version that runs in a browser. Installation options include Opam, Docker, source compilation, and listed Debian, Fedora, and Ubuntu packages. Its graphical interface saves proof attempts and transformations in an XML file and can replay obsolete attempts. Why3 is free and open source under GNU LGPL 2.1 with a special linking exception. Loop invariant inference is a work in progress, and many features remain very limited.