# ucsd-progsys/liquidhaskell

Liquid Types For Haskell

Repository: https://github.com/ucsd-progsys/liquidhaskell
Canonical: https://ross.abutalabs.com/products/liquidhaskell
Language: Haskell
License: BSD-3-Clause
License Family: permissive
Topics: haskell, refinement-types, smt, verification
Last push: 2026-08-24T15:29:44+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 83, longevity 100
- inputs: {"age_days": 5093, "days_push": 9, "days_rel": 118, "gap_med": 15, "n_releases_24m": 6}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1332, forks 162 (observed 2026-08-28T04:04:24.414910+00:00)

## What it is
LiquidHaskell is a formal verification tool that brings refinement types to Haskell via a GHC plugin. It uses the Z3 SMT solver to statically prove properties about Haskell programs at compile time.

## Use cases
- verify Haskell code for correctness at compile time
- add refinement types to Haskell functions
- prove invariants like non-empty lists or sorted vectors
- catch division-by-zero and out-of-bounds errors statically
- formally verify library code written in Haskell

## When to choose
- you write Haskell and want machine-checked correctness guarantees
- you need to encode and prove pre- and post-conditions on functions
- you want to eliminate certain runtime errors without dynamic checks

## When to avoid
- you work in languages other than Haskell
- you need lightweight type checking without SMT solver setup
- your build cannot tolerate extra verification time or a Z3 dependency

## Facets
- artifact type: library
- maturity: active
- function: type-system, testing, security
- domain: programming-languages, developer-tools
- platform: windows, cli
- tags: haskell, refinement-types, formal-verification, smt-solver, ghc-plugin, liquid-types, algorithms, linux, macos

## Member repositories
- ucsd-progsys/liquidhaskell (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:24.414910+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T04:45:14.167747+00:00, confidence not recorded.
  - readme: https://github.com/ucsd-progsys/liquidhaskell (fetched 2026-08-28T04:04:24.414910+00:00, sha 17b21db8396d)
- Data as of 2026-08-30T08:39:29.467469+00:00.