The Lettuce programming language and compiler/interpreter

Lettuce is a new functional programming language with a simple static type system. This repository contains its corresponding MLIR/LLVM based compiler/interpreter: lettucec.

Example lettuce code that checks if a number is even or odd:

let
    def isEven(n: i32) -> bool =
        if n == 0 then
            true
        else
            isOdd(n - 1)

    def isOdd(n: i32) -> bool =
        if n == 0 then
            false
        else
            isEven(n - 1)
in
    isEven(31)

Demo of compiler mode:

~/dev/lettuce/build/lettucec
❯ cat ../../examples/print.lettuce                  # Print out the contents of print.lettuce
let i = 1 in print(4)
~/dev/lettuce/build/lettucec
❯ ./lettucec ../../examples/print.lettuce           # Compile print.lettuce
Wrote output.o
❯ clang++ output.o -o output                        # Link generated object file
❯ ./output                                          # Execute the generated binary `output`
4

Demo of interpreter mode:

~/dev/lettuce/build/lettucec
❯ ./lettucec                                        # Start interpreter mode
>>> let i = (1 + 2) * 3 in i + 4                    # ((1 + 2) * 3) + 4
Return value: 13
>>> let i = 4 in print(i)                           # Print out the value of variable i
4
Return value: 3
>>> let h = (|x : i32, y : i32| x + y)(1, 2) in h   # Define a function that adds arguments x and y and call it with arguments x=1, y=2
Return value: 3
>>> CTRL-D                                          # End input

Build

Tested on Ubuntu 22.04 and MacOS Ventura 13.4.1 (c)

Build prerequisites

clang++
cmake
clang-tidy
Ninja/Make
python3
curl

Building

chmod +x build.sh
./build.sh

• This will download/build llvm, lettuce and the unittests.
• build will contain the build artifacts for lettucec and unittests.
• third-party will be populated with the llvm source code.
• third-party/llvm-project/install/ will be where llvm is installed

Run

./build/lettucec/lettucec <path_to_file>
./build/lettucec/lettucec examples/hello.lettuce

Test

./build/unittests/all_tests

Clean

cd build
cmake --build . --target clean

Extra Build Instructions

Incremental builds

• after running build.sh, you can run the following command to rebuild

cd build
cmake --build .

Building Tablegen docs

cd build
cmake --build . --target mlir-doc

Docker

Follow the instructions below if you'd prefer to use a docker container to build the project.

# Build Docker image
docker build . -t lettuce
# Create container and mount current directory in container
docker create -t -i --name lettuce -v $(pwd):/lettuce lettuce bash
# Start the container
docker start -a -i lettuce
# Run build instructions in container

Project structure

Project layout

examples/                   # example lettuce programs
include/                    # headers and tablegen files
include/Romaine/            # IR tablegen files and their headers
lettucec/                   # the lettucec compiler sources
lib/                        # libraries
lib/Romaine                 # IR tablegen files and their sources
third-party/                # contains llvm source and install
unittests/                  # contains googletest unittests

• CMake files are in each directory and generally correspond to a project
• For example, lettucec/CMakeLists.txt is the cmake file for the lettucec compiler and declares the lettucec executable as well as the flags used to build it.
• You must add new source files to both the CMakeLists.txt in lettucec and unittests

Tablegen

• each tablegen file corresponds to a header or source file
• For example, RomaineOps.td corresponds to RomaineOps.h
  • after building, RomaineOps.h.inc will be generated in the build directory
  • RomaineOps.h includes this file