MC++

MC++ is an esoteric, command-oriented programming language built using C++ designed to mirror Minecraft server commands as closely as possible.

It supports script execution, an interactive REPL, scoped command blocks, named-argument functions, dynamic / loose typing, and command-based control flow.

Running MC++

• Download the latest build from the releases page
• To start the REPL, simply run the program or call it with mcpp
• To run a mcpp file, use mcpp <file.mcpp>
• To show help, run mcpp --help or mcpp -h
• To show version, run mcpp --version or mcpp -v

Building MC++ from source code

• Building from source code requires Windows, Visual Studio: Desktop Development with C++, and MSVC / MSBuild
• To build in Visual Studio: Open mcpp.slnx, then Build Solution
• To build from terminal: Open Developer Command Prompt for Visual Studio and run: MSBuild.exe mcpp.vcxproj /p:Configuration=Release /p:Platform=x64

REPL

The REPL is an interactive session for performing live commands and seeing output in realtime. The REPL supports multi-line input and persistent session state.

• >>> means fresh input
• ... means current block is still open
• /stop exits REPL session
• :help shows REPL help
• :quit exits the REPL
• :exit exits the REPL

Commands

• /say <expr> evaluates an expression and prints the result
• /give <name> <expr> assigns a value to a variable
• /msg <name> reads one line of input and stores it as string <name>
• /stop halts program
• /function <name> {param1, param2, ...} starts a function, uses /execute store result to return within function scope, and must be within a command block to be multiple lines long. Command block } ends the function definition.
• /function <name> {a: expr, b: expr, ...} calls a function with named arguments
• /execute store result <var> run <command> runs a command and stores that command's result in <var>
• /execute store result <expr> returns a value from inside a function
• /execute if <condition> run <command> runs the command only if the condition is true
• /execute unless <condition> run <command> runs the command only if the condition is false
• /execute until <condition> run <command> keeps running the command until the condition becomes true
• /summon command_block { ... } creates a block, usually used with function definitions
• /gamerule keep_inventory true makes block or function variable changes persist outside that scope
• /gamerule keep_inventory false keeps block or function variable changes local to that scope

Expressions

MC++ supports the following:

• Integers: 67
• Strings: "example"
• Booleans: true or false
• Variable references: x
• Parantheses: (x + 2) * 3
• Unary minus: -x
• Arithmetic: +, -, *, /
• Comparison: ==, !=, <, <=, >, >=

Runtime Behavior

• + performs integer addition when both operands are integers, and otherwise performs string concatenation
• -, *, /, <, <=, >, >= all require numeric values
• Numeric strings can be coerced into numbers
• Division is integer division (no decimal)
• Conditions can use booleans, integers, or strings. Empty string is false, non-empty string is true, but "false" and numeric 0 are treated as false.

Scope Rules

• Top level: variables persist for current script or REPL session
• Command blocks: creates child scope
• Functions: creates child scope
• With keep_inventory active, block/function writes merge back into the parent scope, otherwise local within block/function.