HOL4 vs Z3
HOL4
hol-theorem-prover.orgZ3
github.comSide by side
| Figure | HOL4 | Z3 |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | — | Yes |
| Windows | Yes | Yes |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| Android | — | Yes |
| API | — | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Formal Verification Tools | 8.1 (#9) | 7.4 (#26) |
| License | HOL is free software released under the Modified (3-clause) BSD licence. | The repository states that Z3 is licensed under the MIT license. |
| Purpose | HOL4 is a proof assistant for higher-order logic and a programming environment for proving theorems and implementing proof tools. | Z3 is a theorem prover and satisfiability modulo theories (SMT) solver. |
| Support | The community offers help through a mailing list and Zulip chat, while bug reports and feature suggestions go to GitHub issues. | The project wiki says to contact the creator of an external binding package for support issues. |
Plans
In their own words
HOL4
HOL4 is a free, interactive proof assistant for higher-order logic, with a programming environment for proving theorems and building proof tools. It supports work that combines deduction, execution, and property checking. Built-in decision procedures and theorem provers can establish many simple theorems, and an oracle mechanism can connect to external programs such as SMT and BDD engines. HOL4 supports higher-order logic and Standard ML, and can produce proof artifacts and counterexamples. It is self-hosted and listed for Linux, macOS, and Windows. A Standard ML compiler is required, with Poly/ML recommended; Moscow ML and MLTon are also supported for building tool executables. Windows installation can use Cygwin or the Windows Linux subsystem with Poly/ML. Moscow ML is another option, but the Windows guide notes that it is slower, lacks some Poly/ML libraries, and cannot run concurrent Holmake builds. HOL includes Emacs modes for syntax display and session interaction, and the installation guide links to Vim plugin documentation. Online materials include a tutorial, quick reference, FAQ, manuals, and generated indexes.
Z3
Z3 is a theorem prover and satisfiability modulo theories (SMT) solver used in software verification and analysis. SMT-LIB2 is its default input format, and it supports the SMT-LIB format. The project documents bindings or APIs for C, C++, .NET, Java, Go, OCaml, Python, Julia, and JavaScript/TypeScript. Z3 can be built with CMake, vcpkg, or Bazel, and the repository links to pre-built binaries for stable and nightly releases. A project wiki also links to a page for trying Z3 in a browser. It supports proof artifacts and counterexamples, and listed input languages include SMT-LIB2, Rust, Smalltalk, and several of the languages with documented APIs. Z3 is MIT licensed, with downloads and source code available at no charge. Python is required to build it; additional toolchains are needed for Java, .NET, OCaml, and Julia APIs. The README says MSVC builds enable Control Flow Guard and Address Space Layout Randomization by default.