efci - Effective Curry Interpreter

This repository contains the implementation of efci, a Curry interpreter based on effects and handlers.

Installation (tested with stack 3.7.1 and cabal 3.16.1.0)

git clone https://github.com/nbun/efci
cd efci
git submodules pull --init
stack install

Usage

Run

efci [filename]

from the directory where filename.curry is located. If efci is called without an argument, only the Prelude module is loaded. If you have rlwrap installed, use rlwrap efci [filename] to get an input history for the interpreter.

Options

• Without an option, the input is interpreted as a Curry expression within the loaded file.
• :q exits interpreter.
• :o rotates between the available interpretation modes
• :time toggles printing time elapsed during interpretation
• :fcy toggles printing of the main expression generated from the input.

Run tests

stack test effective-curry-interpreter

Run benchmarks

stack bench effective-curry-interpreter

Generate documentation

stack haddock --open effective-curry-interpreter

Repository structure

• src: implementation of the interpreter(s)
  • Data.Union: open unions used for implementing signatures
  • Effect: implementations of (Curry-specific) effects
    • FlatCurry: Curry-specific effects
      • Constructor: terms and pattern matching effect
      • Declarations: function declaration effect
      • Function: Partial application effect
      • IO: input/output effect
      • Let: local bindings effect
    • General: commonly known effects
      • Error: (unexpected) error effect
      • Memoization: lazy evaluation effect
      • ND: non-determinism effect
      • State: state effect
    • Transformation: transformation functions
      • AE2Result: transformation from effects to results
      • FCY2AE: transformation from FlatCurry to effects
    • App: REPL logic and front end integration
    • Debug: flags for toggling debug output
    • Forwarding: forwarding functions and carrier classes
    • Free: effect representations (tree-based, continuation-based, smart views)
    • InterpFL: implementation of A Monadic Semantics for Core Curry
    • Pipeline: pipelines for different effect representations
    • Signature: adapters, type operators, and injection functions for signatures
    • Type: auxiliary functions and type definitions
• tests/Main.hs: test suite runner
• examples: example programs for the test suite
• benchmarks: benchmark programs
  • Main.hs: benchmark runner

Known issues

• Ambiguous types are not defaulted. For example, 1 + 2 needs to be annotated as 1 + 2 :: Int.
• Not all external functions are implemented.

Historic releases

Haskell'24 paper Making a Curry Interpreter using Effects and Handlers:

• 4db98c2 for the original interpreter
• 1421632 for an extended version featuring unification
• 90dfb99 for 'fusion all the way'