CMinusMinus - The Other Side Of the Number Line

Hundreds of hours went into brainstorming that unique name for my language. Phew, who would have thought of that. CMinusMinus is just a dynamically typed, interpreted and a very unoptimized toy language that I used to learn how interpreters work. Currently it's very simple language with REPL playgroud.

Preview

cmm_preview.mp4

Working

The working of the interpreter will give a brief idea about how it works and it's architecture:

• Lexer: The input code is fed into the lexer that performs lexical analysis of our code and outputs our code as a list of small workable data structures called tokens.
• Parser: The output from the lexer is picked up by the parser that parses our code and generates an abstract syntax tree. We have achieved this by implementing a pratt parser.
• Pratt Parser: The appropriate parsing function is associated with very node in our AST, depending whether the token is found in a prefix or an infix expression.
• Evaluation: Traverse the AST, visit each node and do what the node signifies. It's called tree-walking interpreter.
• Object System: Every value in our code is an Object. Each value in our environment is wrapped inside a struct which fufills this Object interface. We have used an object system to represent the internal values instead of primitive types.
• Garbage Collection: Golang handles garbage collection under the hood. To implement a garbage collection system we will need to bypass golang's garbace collection which is not possible.

Variables

You can use let keyword declare let statements. The supported primitives are int64 and boolean. The interpreter will dynamically assign the types with let.

  let x = 4;

Everything is an expression in CMM. In the above example, let x = 4; produces a value of 4;

Functions

You can declare functions with the fn keyword.

let add = fn(a,b) {return a+b;}

REPL

You can exit the REPL by using exit() command.

Todo Features

• Replace let with static types.
• Add Strings and character primitives
• Arrays
• Standard i/o functions for cli
• Networking Capabilities

Installation

• Clone the repository.
• Navigate into the source code and run ./build.sh.
• If shows permission errors: chmod a+x ./build.sh.
• Now run ./build.sh again the go will build the code binary in the bin/ directory.
• Run ./bin/cminusminus and you will enter the REPL.