he++

An interpreted general-purpose programming language built on top of golang.

The purpose of this project is to learn how to build a programming language from scratch. It is not meant to be used in the real world, and can thus have all kinds of whacky features.

Quick Start

• Clone the repository
• Setup the .env fild taking reference from the .env.example file
• Run the main.go file to see the interpreter in action (it executes a sample program in the samples folder)
• There are many sample programs in the samples directory to try out
• The file to be executed can be specified in the .env file
• A command line interface will be implemented soon

REPL

To be implemented soon

Features

Variables

• declare a variable using the let keyword
• the let keyword is optional

Template Strings

to be implemented soon

Conditionals

• Support for if, else if, else statements
• parentheses around the boolean expression are optional

if(true){

} elseif(5<7){

}else{
    
}

Loops

• Support for a basic loop structure with break statement
• parentheses around the boolean expression are optional

loop(boolean_expression){
    //statements
    if(condition){
        break;
    }
}

Functions

Support for functions with return values and arguments Arguments are passed by value All functions in a scope are hoisted to the top of the scope. Recursion is supported.

function add(a,b){
    return a+b;
}

let k=add(5,6);

Some natively implemented functions are available in every scope, like:

• print and println : Prints the argument to stdout.
• readNumber : Returns a number scanned from stdin.
• len : Accepts an array or string and returns its length.
• makeArray : Accepts a size and returns an array of that size, populated with nulls.
• random : Returns a pseudo-random number between 0 and 1.

Arrays

An array can have any number of elements of any type, including other arrays. There can be a trailing comma after the last element.

let arr=[1,2,3,4,[5,6,7],"hello world!",];

Objects

Objects behave exactly like those in javascript, with the dot operator to access properties.

let obj={
    name:"John",
    age:25,
    address:{
        city:"New York",
        country:"USA"
    }
};  
let name=obj.name;
let city=obj.address.city;

Peculiarities

None!

Bugs

• unassigned array is not cleaned up when scope is exited
• line numbers in error messages are not correct
• lexer can be hugely improved.

Notes

• The VM runs on 1kb of memory.

TODO

• Implement template strings
• Implement objects (dot operator)
• Implement tuples (comma operator)
• implement module system and imports
• improve memory management
• implement default args to function
• implement variadic args to function

Contemplating