Install the Haskell SDK

Prerequisites

GHC 9.12.2 and Cabal (the binding builds with cabal-version: 3.8). The FFI backend also needs a Rust toolchain when building libpanproto_c from source; rustup is recommended.

The panproto package currently lives under bindings/haskell/; build it from the repository. The default rust flag links the FFI backend against libpanproto_c, so the library has to be staged first. There are two ways to get it.

Build from source

bootstrap/dev-link.sh builds panproto-c from the workspace with cargo build -p panproto-c --release, compiles the panproto-glue C layer into a standalone libpanproto_glue.a, and stages both under bindings/haskell/.panproto-c/. It then writes a gitignored cabal.project.local carrying the absolute lib and include paths (cabal’s relative extra-lib-dirs propagate into ghc-pkg’s registration metadata, which rejects anything but absolute paths).

git clone https://github.com/panproto/panproto.git
cd panproto/bindings/haskell
./bootstrap/dev-link.sh                # builds panproto-c, stages libs
cabal build
cabal test

Run dev-link.sh again after every change to panproto-c, to the C glue, or to the workspace Cargo.toml.

Prebuilt binaries

bootstrap/fetch-bindist.sh [version] downloads the prebuilt libpanproto_c for the host platform from the corresponding GitHub Release (it detects aarch64-apple-darwin, x86_64-apple-darwin, x86_64-unknown-linux-gnu, and aarch64-unknown-linux-gnu), rebuilds the C glue against the fetched header, and writes the same cabal.project.local. No Rust toolchain is needed on this path.

git clone https://github.com/panproto/panproto.git
cd panproto/bindings/haskell
./bootstrap/fetch-bindist.sh v0.72.0   # pass the release tag that matches this checkout
cabal build
cabal test

Pass the release tag explicitly. The script’s fallback tag can lag the package version in a development checkout.

Native-only (no FFI)

For the pure-Haskell subset, disable the foreign-function interface (FFI) backend. This build needs no libpanproto_c and no Rust toolchain:

cabal build -f-rust

Verification

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DuplicateRecordFields #-}

import qualified Panproto.Schema as S

main :: IO ()
main = do
    let s = S.buildSchema "geojson" $ do
                S.vertex S.Vertex {S.id = "post", S.kind = "record", S.nsid = Nothing}
    print (S.vertexCount s)

Place the example in an executable component or load it in cabal repl. Building a one-vertex structured schema and printing its vertex count exercises the pure value algebra without touching the engine, so the example also works with the FFI backend disabled.

Common mistakes

Some Python distributions, including Anaconda, put an older ld on PATH. On macOS arm64, that linker cannot read GHC’s response-file syntax and reports ld: file not found: @<tmp>/ghc_tmp_*.rsp. dev-link.sh warns when ld is not the system linker. Prepend /usr/bin to PATH and retry.
Skipping the bootstrap step on a default (rust-flag) build. Without dev-link.sh or fetch-bindist.sh, no cabal.project.local exists, extra-lib-dirs is unset, and the link fails on the missing libpanproto_c.
A relative extra-lib-dirs. The path in cabal.project.local is absolute by design; ghc-pkg refuses a relative one during package registration.

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