Functional Programming Language based on Lambda Calculus highly inspired by this video Programming with Math | The Lambda Calculus - Eyesomorphic made from scratch, entirely in C++.

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Getting Started

Prerequisites

• CMake (version 3.16+ recommended)
• Python 3.8+ (for development environment and tooling)
• A C++17 capable compiler (e.g. g++, clang++, or MSVC on Windows)

Setup

GNU/Linux

bash ./scripts/setup.sh

Windows (PowerShell)

. .\scripts\setup.ps1

Tests

python tests/tests.py

Samples

Booleans and If-Then construct built entirely using Lambda Expressions.

true: Bool = \x: Any. \y: Any. x
false: Bool = \x: Any. \y: Any. y

if: Any = \condition: Any.
    \thenClause: Any. \elseClause: Any.
        (condition thenClause elseClause)

boolToString: Bool = \bool: Bool. (if bool "true" "false")

(print (boolToString true) "\n")
(print (boolToString false) "\n")

$ ./cmake-build-debug/lbd -f  ./examples/conditional_branching.lbd
true
false

Shapes Demo

-- Define Pi as constant
pi: Float = 3.14

-- Define function to calculate square
square: Float -> Float = \x: Float. (mul x x)

-- Define function to calculate area of circle
areaOfCircle: Float -> Float = \r: Float.
    (mul pi (square r))

-- Define function to calculate volume of cylinder
volumeOfCylinder: Float -> Float -> Float = \r: Float.
	  \h: Float. (mul (areaOfCircle r) h)

-- Calculate the volume of a cylinder
(print "Volume of cylinder is: " (volumeOfCylinder 5.0 10.0) "\n")

$ ./cmake-build-debug/lbd -f ./examples/shapes.lbd
Volume of cylinder is: 785.000000

Fibonacci

fibonacci: Any = \num: Float.
    (null (cmp 0 num) 0
        (null (cmp 1 num) 1
            (add (fibonacci (sub num 1.0)) (fibonacci (sub num 2.0)))))

(print (fibonacci 10))

$ ./cmake-build-debug/lbd -f ./examples/math_demos.lbd
55.000000

Usage

After building, you can run the interpreter with:

lbd [options]

Options

-f, --file <filepath>   Specify input source filepath to run
-h, --help              Show this help message and exit
-d, --debug             Enable debug mode
-r, --repl              Run in interactive REPL node
--docs                  Generate language-reference-document

Generate the language-reference-document by using the --docs flag, and use it as the source of truth for native-function-signatures.

Editor Plugins

1. GNU Emacs

TODO

• TODO: Add better examples (e.g., Advent of Code snippets).
• TODO: CI/CD for testing.
• TODO: Fix tests output in README.
• TODO: Step debug kind of functionality in REPL. Inside REPL, while loading a file, load one expression at a time and provide user with some feedback and actions to perform.
• TODO: Make a pre-commit-hook which does not allow to push to master, if the tests are failing. Additionally, test whether the docs/SIGNATURE.txt is up-to-date or not.