makrell-code

name	makrell-code
description	Write and explain code in MakrellPy, MakrellTS, and Makrell#. Use when creating, editing, or understanding Makrell-family source files (.mrpy, .mrts, .mrsh).
allowed-tools	Read Grep Glob Edit Write Bash

Makrell Code

You are helping in a project that uses one or more Makrell programming languages. The Makrell family shares a common structural core (MBF) but targets different host ecosystems.

Implementations

Language	Host	File ext	CLI command	Install
MakrellPy	Python	.mrpy	makrell	pip install makrell
MakrellTS	JS/TS	.mrts	makrellts	bun add -g makrellts
Makrell#	.NET / CLR	.mrsh	makrellsharp	dotnet tool install --global MakrellSharp.Cli

Syntax Quick Reference

Expressions, calls, and assignment

2 + 3                           # infix operator
{add 2 3}                       # function call
x = 42                          # assignment

Functions

{fun add [x y]
    x + y}

add3 = {add 3 _}               # partial application with placeholder

Pipes

[2 3 5] | sum                   # forward pipe
sum \ [2 3 5]                   # reverse pipe
2 | {+ 3} | {* 5}              # operator-as-function in pipe

Conditionals

{if (x > 0) "positive" "non-positive"}

{cond
    (x > 0)  "positive"
    (x == 0) "zero"
    true     "negative"}

Pattern matching

{match value
    2
        "two"
    [x=_ y=_]
        x + y
    _:str
        "string"
    _
        "other"}

Macros and meta

{def macro twice [x]
    [{quote $x} {quote $x}]}

{meta
    greeting = {quote "Hello"}}

{def macro hello [ns]
    {quote {print {unquote greeting}}}}

Async/await (all three tracks)

{async fun fetchValue [value]
    {await {Promise.resolve value}}}      # MakrellTS

{async fun just_sleep [n]
    {await {asyncio.sleep n}}             # MakrellPy
    n + 2}

Classes (MakrellPy)

{class Point
    {fun __init__ [self x y]
        self.x = x
        self.y = y}
    {fun dist [self]
        {math.sqrt (self.x ** 2 + self.y ** 2)}}}

Imports

{import math}                             # MakrellPy: import module
{import math@[sin cos]}                   # MakrellPy: import names
{import System.Text}                      # Makrell#: import CLR namespace
{import System.Text@[Encoding]}           # Makrell#: import specific type

CLR interop (Makrell# specific)

{new StringBuilder ["Mak"]}
{sb.Append "rell#"}
{sb.ToString}
{new (list string) ["a" "b"]}            # generic types
{Enumerable.Repeat@(string) "ha" 3}      # explicit generic call

Operator Precedence (high to low)

Operator	Precedence	Description
.	200	member access
**	100	exponentiation
*, /	90	multiplication, div
+, -	80	addition, subtraction
`	>`	40
`	`	30
\	30	reverse pipe
==,!=	20	equality
<,>	20	comparison
and	15	logical and
or	10	logical or
=	5	assignment

Operators are extensible via {def operator}.

Guidelines

When writing Makrell code:

• Use curly braces {} for calls, not parentheses: {f x y} not f(x, y)
• Use square brackets [] for lists and parameter lists: [2 3 5], {fun f [x y] ...}
• Use pipes for data flow — prefer xs | {map f} | sum over nested calls
• Use _ for partial application — {add 3 _} creates a function awaiting one argument
• Indent body forms under their head — the indentation is significant for readability
• Operators can be used as functions — {+ 3} is a function that adds 3
• Pattern matching replaces chains of if/else — prefer {match ...} for structural dispatch
• Prefer pipeline style for sequential transformations

When explaining Makrell code:

• Relate to the user's host ecosystem (Python, JS/TS, or .NET)
• Point out which features are family-wide vs implementation-specific
• Note operator precedence when it affects expression grouping

Documentation

• MakrellPy: https://makrell.dev/makrellpy/
• MakrellTS: https://makrell.dev/makrellts/
• Makrell#: https://makrell.dev/makrellsharp/
• Shared concepts: https://makrell.dev/concepts/
• Playground (MakrellTS): https://makrell.dev/playground/