Makrell

Makrell is a family of programming languages implemented in Python. It consists currently of these languages:

MakrellPy, a general-purpose, functional programming language with two-way Python interoperability, metaprogramming support and simple syntax.
MRON (Makrell Object Notation), a lightweight alternative to JSON.
MRML (Makrell Markup Language), a lightweight alternative to XML and HTML.
Makrell Base Format (MBF), a simple data format that forms the basis for both MakrellPy, MRON and MRML.

The project is in an early stage of development and is not yet ready for production use.

Quick Start

Installation

pip install makrell

MakrellPy REPL usage

makrell
> 2 + 3
5
> [2 3 5] | sum
10

Run a MakrellPy script

makrell myscript.mr

IDE Support

MakrellPy is supported by the MakrellPy Language Server, included in the Makrell package. The language server is based on the LSP protocol and can be used with any LSP-compatible editor, such as Visual Studio Code, Sublime Text, Atom, Vim, Emacs etc. A VS Code extension is available here.

MakrellPy

The following is a quick introduction by example to the MakrellPy language. See examples and tests for more code examples.

Syntax

MakrellPy uses the Makrell Base Format as its base syntax (see below). MakrellPy-specific syntax is built on top of this. The following is a simple example of a MakrellPy program:

# This is a comment.
a = 2
b = a + 3
{sum [a b 5]}  # function call
[a b 5] | sum  # function call by pipe operator
sum \ [a b 5]  # function call by reverse pipe operator

# Conditional expression
{if a < b
    "a is less than b"
    "a is not less than b"}

# Function definition
{fun add [x y]
    x + y}

# Partial application
add3 = {add 3 _}
{add3 5}  # 8

# Operators as functions
a = 2 | {+ 3} | {* 5}  # 25

# Custom operators with precedence levels
{operator 😐 100
    $left + $right + 1}
{operator 😵 90
    $left - $right}
a = 2 😵 3 😐 5
a | print
{assert a == -7}
b = 2 | {😐 3}
b | print
{assert b == 6}

# A macro that composes a sequence of functions
{macro pipe [ns]
    ns = {regular ns}
    p = ns@0
    i = 1
    {while i < {len ns}
        p = {quote {unquote p} | {unquote ns@i}}
        i = i+1
    }
    p
}
f = [x] -> x * 2
mul = [x y] -> x * y
c = {pipe 3 f f {mul 10 _} f f}  # 480

Note:

The syntax is determined by lists and binary expressions.
Return values are implicit, i.e. the last expression in a block is the return value.

Other Features

See the examples and tests directories for examples of the following features:

Class definitions
String interpolation
Function composition
Meta programming, including macros, custom operators and embedded mini-languages
Python interoperability

TODOs, wishlist and ideas

More built-in functions, operators, data types etc.
Fix bugs
Various missing Python features, such as decorators, yield and async/await
Basic typing or type hints as in Python
Pattern matching and destructuring
More advanced typing, possibly with inference and unified with pattern matching and grammar expressions in some mini-language
Better error messages and better IDE support
More documentation and examples
Compilers and code generators for other languages and platforms
A composable query language for heterogeneous sources, such as databases, object structures, web services etc.
Mini-languages for regular expressions and BNF
An API for traversing and transforming MBF trees
A templating language
A website with tutorials, documentation and a playground
Implementations in other languages

MRON

Sample MRON document:

owner "Rena Holm"
last_update "2023-11-30"

books [
    {
        title  "That Time of the Year Again"
        year   1963
        author "Norton Max"
    }
    {
        title  "One for the Team"
        year   2024
        author "Felicia X"
    }
]

The above code corresponds to the following Python dictionary tree:

{
    "owner": "Rena Holm",
    "last_update": "2023-11-30",
    "books": [
        {
            "title": "That Time of the Year Again",
            "year": 1963,
            "author": "Norton Max"
        },
        {
            "title": "One for the Team",
            "year": 2024,
            "author": "Felicia X"
        }
    ]
}

It's possible to embed MakrellPy code in MRON documents, and vice versa. Example:

a 2
b {$ 3 + 5 }

This will be evaluated to this Python dictionary:

{
    "a": 2,
    "b": 8
}

MRML

Sample MRML document:

{html
    {head
        {title A Test}
    }
    {body
        {h1 This is a Test}
        {p [style="color: red"] Just some {b bold} text here.}
    }
}

The above code corresponds to the following HTML:

<html>
    <head>
        <title>A Test</title>
    </head>
    <body>
        <h1>This is a Test</h1>
        <p style="color: red">Just some <b>bold</b> text here.</p>
    </body>
</html>

It's possible to embed MakrellPy code in MRML documents, and vice versa. Example:

{a [b = {$ [2 3 5 7] | sum}] asd}

This will be evaluated to:

<a b="17">asd</a>

Makrell Base Format

The Makrell Base Format is a simple data format that forms the basis for both MakrellPy, MRON and MRML. It is a simple text-based format that is easy to read and write. It is designed to be easy to parse and generate, and to be easy to work with in a text editor.

These element types are supported:

Identifier: A simple name. Examples:
- x
- Y1
- $Example_Æ23.
String: A sequence of characters surrounded by double quotes. The backslash character is used to escape double quotes and backslashes. A string may have a suffix that specifies an implementation-specific data type. Examples:
- "Hi."
- "This is a string: \"Hi.\""
- "2024-02-02"date : a date
- "12AF"hex : a hexadecimal number
Number: A numeric value. As with strings, a number may have a suffix that specifies an implementation-specific data type or value. Examples:
- 42
- 2.5e9
- 2.5G = 2,500,000,000
- 2pi = 6.283185307179586
List: A sequence of elements, surrounded by brackets and usually separated by spaces. Lists may be nested. There are three types of lists:
- "Round", e.g. (2 3 5)
- "Square", e.g. ["a" "b" "c"]
- "Curly", e.g. {asd qwe zxc}
Operator: A symbol consisting of one or more non-alphanumeric characters. Examples:
- +
- ==
- |*
- <*>

For parsing purposes, the following element types are also defined:

Whitespace: A sequence of space, tab and newline characters.
Comment: A sequence of characters that is ignored by the parser. A line comment starts with a # character and continues to the end of the line, while a block comment starts with /* and ends with */.
Other Token: A sequence of characters that does not match any of the other element types.

In addition, the following element type is defined in the core library:

Binary Expression: An operator with two operands.

License

Makrell is developed by Hans-Christian Holm and licensed under the MIT License. See LICENSE for details.

hcholm / makrell-py