def main(args) => "Welcome to Lavender!"

Lavender is a pure functional programming language that takes inspiration from primarily Python and Scala.

Why Use Lavender?

• Simplicity - Lavender relies only on function evaluation, eschewing mutable state and complex control flow in favor of simple, declarative function application. Conditional primitives are supported via piecewise function definition, or standard library functions may be used.
• Immutability - Values may never be modified, and there are no unsafe functions that mutate hidden state. Side effects such as IO and global state are provided via standard library abstractions.
• Clarity - Lavender aims to have an intuitive syntax and standard library that leverage popular notation rather than strict mathematical precision.
• Referential transparency - Every terminating expression has a well-defined value that may be lazily evaluated or aggressively folded. Lavender supports opt-in lazy evaluation through the use of by-name expressions.
• Locality - There are no nonlocal control mechanisms in Lavender. Error states and branching in general are expressed with recursion and composition.

Installation

1. To get started with Lavender, first clone the repository and download the Lavender standard libraries.

   $ git clone --recursive https://github.com/kvverti/clavender.git <PROJECT_DIR>
   $ cd <PROJECT_DIR>
   

   If you have not set up a GitHub SSH key, updating the submodules will not work directly. In this case, you may clone the standard libraries directly into the stdlib folder.

   $ git clone https://github.com/kvverti/lavender-stdlib.git <PROJECT_DIR>/stdlib
   

2. Run make to compile the project. Building Lavender requires a C compiler to be installed.

3. Assuming the build is successful, run Lavender using the following command.

   $ ./lavender
   

   You should see something like the following.

   Lavender runtime v. 1.0 by Chris Nero
   Open source at https://github.com/kvverti/clavender
   Enter function definitions or expressions
   >
   

   If an error about being unable to find the standard library appears, make sure that the stdlib subfolder contains Lavender source files.

Using the Interpreter

Lavender can run programs from files, or run as a REPL (read-eval-print loop). On the command line, run ./lavender --help for a list of command line options.

REPL Mode

If no run file is passed to Lavender, it will open a REPL. In the REPL, the user can enter expressions or function definitions. Entering an expression will fully evaluate its value and print the result. Function definitions can be later referred to by their simple names.

The REPL will normally take a single line of input at a time. However, the REPL will continue to take lines if there are unclosed parentheses or braces.

Examples:

> "hello, world!"
hello, world!
> def func(a) => str(a) ++ " is really neat!"
repl:func
> func("Lavender")
Lavender is really neat!
> (
>    "multiline input" ++
>    " is great"
>    )
multiline input is great

Running Files

Lavender can also evaluate a file passed on the command line. The first non-option argument to the interpreter is treated as the relative path to the file to run (sans the .lv extension). Any remaining arguments are forwarded to the runtime as strings, and may be accessed from the running program.