ghci

A crate to manage and communicate with ghci sessions.

let mut ghci = Ghci::new()?;
let out = ghci.eval("putStrLn \"Hello world\"")?;
assert_eq!(out, "Hello world\n");

Platform support: Unix only (Linux, macOS, BSDs).

Features

Type conversions

Convert between Rust and Haskell values with ToHaskell / FromHaskell, and evaluate expressions directly into Rust types with eval_as:

use ghci::{Ghci, ToHaskell, FromHaskell};

let mut ghci = Ghci::new()?;

let x: i32 = ghci.eval_as("1 + 1")?;
assert_eq!(x, 2);

// Built-in support for common types
assert_eq!(true.to_haskell(), "True");
assert_eq!(Some(42u32).to_haskell(), "(Just 42)");
assert_eq!(vec![1u32, 2, 3].to_haskell(), "[1, 2, 3]");

Derive macros

With the derive feature, automatically derive conversions for your own types:

use ghci::{ToHaskell, FromHaskell};

#[derive(ToHaskell, FromHaskell)]
struct Point { x: u32, y: u32 }
// Point { x: 1, y: 2 } <-> "Point {x = 1, y = 2}"

#[derive(ToHaskell, FromHaskell)]
#[haskell(style = "app")]
struct Pair(u32, bool);
// Pair(1, true) <-> "(Pair 1 True)"

See the derive macro docs for all supported attributes (name, transparent, style, skip, bound).

Configuration

Use GhciBuilder to configure the ghci session:

use ghci::GhciBuilder;

let mut ghci = GhciBuilder::new()
    .ghci_path("/usr/local/bin/ghci")
    .arg("-XOverloadedStrings")
    .working_dir("/path/to/project")
    .build()?;

Timeouts

use std::time::Duration;

ghci.set_timeout(Some(Duration::from_secs(5)));

Shared sessions

SharedGhci provides a thread-safe, lazily-initialized session for use in tests:

use ghci::{Ghci, SharedGhci};

static GHCI: SharedGhci = SharedGhci::new(|| {
    let mut ghci = Ghci::new()?;
    ghci.import(&["Data.Char"])?;
    Ok(ghci)
});

let mut ghci = GHCI.lock();
let out = ghci.eval("ord 'A'").unwrap();
assert_eq!(out, "65\n");

See the docs for the full API.

License

MIT License

Copyright 2023 Basile Henry