Hello World

Calor is designed to be written by AI agents, not humans. This guide shows you how to instruct an AI to generate Calor code—you won't be writing Calor yourself, but understanding the output helps you verify that contracts match your intent.

Prerequisites

Before starting, set up a Calor-enabled project:

Bash
dotnet new console -o HelloApp
cd HelloApp
calor init --ai claude

This creates:

  • CLAUDE.md - Instructions telling Claude to write all new code in Calor
  • Hook configuration - Automatically blocks .cs file creation, enforcing Calor-first
  • Skills - Syntax reference Claude can consult when needed

Your First Prompt

Open Claude Code in your project directory and simply ask:

Plain Text
Write a hello world program that prints "Hello from Calor!"

That's it. Claude automatically writes Calor code because:

  1. CLAUDE.md instructs it to use Calor for all new code
  2. The hook blocks any attempt to create .cs files

What the AI Generates

Claude creates Program.calr:

Plain Text
§M{m001:HelloApp}
§F{f001:Main:pub}
  §O{void}
  §E{cw}
  §P "Hello from Calor!"
§/F{f001}
§/M{m001}

You don't need to understand every detail of this syntax - the AI handles it. But here's a quick breakdown:

LineWhat It Does
§M{m001:HelloApp}Declares a module (like a C# namespace)
§F{f001:Main:pub}Declares a public function named Main
§O{void}The function returns nothing
§E{cw}The function writes to console (cw = console write)
§P "Hello..."Prints the message
§/F{f001} §/M{m001}Close the function and module

Build and Run

Bash
dotnet build
dotnet run

Output:

Plain Text
Hello from Calor!

Generated C#

Behind the scenes, the Calor compiler transforms your code into C#:

C#
// <auto-generated>
// This file was generated by the Calor compiler.
// </auto-generated>

namespace HelloApp
{
    public static class Program
    {
        public static void Main()
        {
            System.Console.WriteLine("Hello from Calor!");
        }
    }
}

This file is placed in obj/calor/ and compiled automatically by MSBuild.

More Examples

Function with Input

Prompt:

Plain Text
Write a greet function that takes a name parameter and prints a greeting.

Claude generates:

Plain Text
§M{m001:Greeter}
§F{f001:Greet:pub}
  §I{str:name}
  §O{void}
  §E{cw}
  §P (+ "Hello, " name "!")
§/F{f001}
§/M{m001}

Function with Return Value

Prompt:

Plain Text
Write a function that adds two integers and returns the result.

Claude generates:

Plain Text
§M{m001:Math}
§F{f001:Add:pub}
  §I{i32:a}
  §I{i32:b}
  §O{i32}
  §R (+ a b)
§/F{f001}
§/M{m001}

Function with Contracts

Prompt:

Plain Text
Write a divide function that takes two integers a and b,
requires b is not zero, and returns a / b.

Claude generates:

Plain Text
§M{m001:SafeMath}
§F{f001:Divide:pub}
  §I{i32:a}
  §I{i32:b}
  §O{i32}
  §Q (!= b 0)
  §R (/ a b)
§/F{f001}
§/M{m001}

The §Q (!= b 0) is a precondition - the compiler generates runtime checks to enforce this contract.

Why AI-Generated?

Calor's syntax is optimized for AI agents:

  1. Unambiguous structure - Every block has explicit open/close tags with IDs, eliminating brace-matching errors
  2. Explicit contracts - Preconditions and postconditions are first-class, not comments
  3. Declared effects - The AI must declare what a function does (console, network, database)
  4. Lisp-style expressions - (+ a b) is unambiguous; no operator precedence confusion

You describe what you want; the AI handles the how.

Next Steps