RAT

Authors: Alex Alvarez, Riley Kehoe, Chris Beaudoin, Sam Prosser, Carter Esparza

Website

https://rat-language.github.io/

Language Specification

1 Introduction

Originally, following a decent amount of Pythonic structure, we began thinking of naming our child after some of the great Snake languages. However, having noticed how popular Python is for its legibility, yet its overall lack of exciting performance, we began to brainstorm ways to leave the Snake game behind. Thus birthing RAT. See, being created from a small group of LMU Computer Scientists, we understand our position as the small language in this wide world of Programming. Yet, unlike in the natural world, we are no prey. We are a: Really. Awesome. Team.

2 Formal Specification

3 Language Description

(2.1) PROGRAMS: Programs written in rat will consist of one or more statements

int i = 0;        # variable declaration
while (i <= 10){      # While statement
  print(i);           # print statement
  i += 1;             # augmented assignment statement 
}

(2.2) VALUES & TYPES: So far, our language supports the following types:

• int of binary formatted signed values
• float of binary64 values
• str a string literal array of characters
• bool boolean value of true or false
• [Type] array of a specified type
• { Type:Type } dictionary of a specified key:value pair types
• none Null value
• Type? Optional Type utilized for values which may take on none
• Type^ Promise Type to be used with asynchronous functions

bool u = false;
int v = 1;
float w = 2.0;
str x = "three";
[int] y  = [4,5];
{str:float } z = { "six":6.0, "seven":7.0 };

(2.3) DECLARATIONS: Rat language supports declarations which bind identifiers to one of the following:

• Variable (const or var)
• Function
• Parameter Both variables and parameters are formatted with the identifier and the types separated by a colon. Functions are declared similar to how C declares functions, with the return type followed by the identifier, followed by it's parameters and a block containing 0 or more statements.

float foo(x:float, y:float){    # function + parameter declaration
  return x**2 + y**2;
}

float z = foo(3.0, 4.0);   # variable declaration
const float w = sqrt(z);        # constant variable declaration

(2.4) STATEMENTS: The following statements are supported in rat language (an example is given for each):

• Declarative statements: see above
• Return statements: return value;
• Assignment statements: x = value;
• Augmented Assignment statements: x += 1;
• Pass statements: pass;
• Break statements: break;
• Try Statements: try{ pass; } catch(e:str){print(e);}
• Control Flow Statements: see below

(2.5) CONTROL FLOW: Rat language provides the for-in & while loops as well as conditional if statements

• While Loops: while (i < 4){print(i); i+= 1;}
• For loop (Iterable Objects/expressions): for i in iterable{print(i);}
• For loop (Inclusive range): for i in 0...5{print(i);}
• For loop (Exclusive range): for i in 0..<5{print(i);}
• Conditional statements: if false{ pass; } else if false { pass; } else { pass; }

(2.6) EXPRESSIONS:

• Booleans : true, false
• None: none e.g. no value
• Negation: -x
• Logical NOT: !x
• Await: await <<1200>> foo()
• Logical OR: x || y
• Logical AND: x && y
• Relational: <=, <, ==, !=, >=, >, non-associative
• Additive: x - y,x + y, Left associative
• Multiplicative: x * y,x / y,x % y Left associative
• Exponentiation: x ** y Right associative

Features

As a statically typed language, we aim to take Python to the next level. By enforcing set types for variables and functions, we offer a better overall performance than Pythonic languages. Further, adapting whitespace with simple, yet elegant bracketing, we leave no room for confusion when designing loops, functions, and statements.

Examples

Each example will be posted in Rat followed by its JavaScript equivalent.

Hello World

helloWorld.rat

print("Hello, World");

helloWorld.js

console.log("Hello, World");

FizzBuzz

fizzBuzz.rat

void fizzbuzz(n:int){
  for i in 0...n {
  	str fbnum = "";
    if ((i % 3==0) || (i % 5 == 0)){
      if (i % 3 == 0){ fbnum += "Fizz"; }
      if (i % 5==0){ fbnum += "Buzz"; }
  	}else{fbnum = str(i);}
    print(fbnum);
 }
}

// prints fizzbuzz up to 16 in this case
fizzbuzz(16);

fizzBuzz.js

function fizzBuzz(n) {
  for (let i = 1; i <= n; i++) {
    let output = "";
    if (i % 3 === 0) {
      output += "Fizz";
    }
    if (i % 5 === 0) {
      output += "Buzz";
    }
    console.log(output || i);
  }
}

Factorial

factorial.rat

int factorial(n:int){
    int value = 1;
    if (n != 0 && n != 1){
        for i in 2...n {
            value *= i;
        }
    }
    return value;
}

factorial.js

function factorial(n) {
    let result = 1;
    if (n != 0 && n != 1){
        for (let i = 2; i <= n; i++) {
            result *= i;
        }
    }
    return result;
}

Fibonacci Numbers

fibonacci.rat

int fib(n:int){
    // returns the nth value of the fibonacci sequence
    int a = 0;
    int b = 1;
    int c = 0;

    if (n == 0){
        return a;
    }
    for i in 2...n {
        c = a + b;
        a = b;
        b = c;
    }
    return b;
}

fibonacci.js

function fibonacci(n) {
  let a = 0,
    b = 1,
    c;
  if (n === 0) return a;
  for (let i = 2; i <= n; i++) {
    c = a + b;
    a = b;
    b = c;
  }
  return b;
}

Prime Numbers

prime.rat

bool prime(n:int){
    if (n <= 1) { return false; }
    if (n <= 3) { return true; }
    if (n % 2 == 0) || (n % 3 == 0) { return false; }
    int i = 5;
    while i*i <= n {
    	if (n%i==0) || (n%(i+2) ==0) {
        	return false;
        }
        i += 6;
    }
    return true;
}

prime.js

function isPrime(number) {
  if (number <= 1) return false;
  if (number <= 3) return true;
  if (number % 2 === 0 || number % 3 === 0) return false;
  for (let i = 5; i * i <= number; i += 6) {
    if (number % i === 0 || number % (i + 2) === 0) return false;
  }
  return true;
}