The Lemni Programming Language

WARNING: This project is highly experimental and has an unstable development schedule

Lemni is a functional programming language I created for the hell of it. It is designed with the intent of being referentially transparent while still being able to use (some) procedural techniques.

Library

Included is a library for lexing, parsing, evaluating and compiling lemni source code. It has a C11 API with C++20 wrappers. It is implemented in C++20.

For an example of lexing and parsing take a look at testall/main.cpp.

Dependencies

• ICU4C
• GNU MP
• GNU MPFR
• ArbLib
• libffi
• LLVM 10

Ubuntu

sudo apt --no-install-suggests --no-install-recommends install \
  g++ make cmake-data cmake\
  libgmp-dev libmpfr-dev libflint-dev libflint-arb-dev \
  libicu-dev libffi-dev llvm-10-runtime llvm-10-dev

Building

Taking for granted a bash-like shell, from the source dir run the following:

git submodule update --init --recursive
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Debug
cmake --build . -- -j4

REPL

A REPL is included to test out the language quickly.

Building

Follow the instructions under Library

Usage

Command: lemni-repl [options]

Here options can be one or more of the following:

Option	Description
-i filename	Evaluate a file before prompting for user input
-e "expr"	Evaluate an expression and print the result

If run without any options you should get a blank interpreter instance to play around with.

To start the REPL from the build directory, run the following command:

./repl/lemni-repl

You should be met with a prompt like so:

Lemni lang REPL v6.9 rev 420
Enter Repl.help () for help, or Repl.quit () to quit

>

To get a feel for the language, try calling Repl.tut ().

Lemni Example

import IO
import Chars

prompt(msg) =
	IO.out msg
	IO.in ()

capitalize(name) =
	(Chars.toUpper (head name)) ++ (tail name)

stripWs(name) =
	if Chars.isSpace (head name) then
		stripWs (tail name)
	elif Chars.isSpace (last name) then
		stripWs (init name)
	else
		name

main() =
	name = (capitalize . stripWs)
		(prompt "What's your name? ")
	
	IO.outln ("Hello, " ++ name ++ "!")

Special thanks

Thank you to all the developers behind the following open-source projects that made this possible:

• LLVM
• libffi
• ICU4C
• GNU MP
• GNU MPFR
• ArbLib
• UTF8-CPP
• {fmt}
• replxx