Rook

A few months as I was learning about compiler design, I came up with the project Rook. Rook Is a very simple programming language I am making for fun.

Disclaimer:

1. I am not a professional in programming language design. I barely know anything about programming languages.
2. The language is barely tested, therefore its possible that there are tonnes of errors unearthed. For example the error reporter is drunk.
3. Unary operators are not supported yet.
4. I know the compiler is written in C#.

Hello world.

Print("Hello world!");
//Print is an inbuilt function used to print to the console.

Before we dive deep into Rook, A few points are worth noting.

• Variable names can only contain alphabets and an underscore (_) (for now).
• Only decimal numbers are supported (for now).
• Everything in Rook is an object.
• EVERY STATEMENT in Rook returns a value. I mean EVERY STATEMENT even an assingment. An assignment statement returns the currently assigned value

Basic Types

The language has very few basic data types. These are:

1. Numbers.
2. Strings.
3. Booleans.
4. Null.

Numbers

Numbers are, well numbers. All numbers in Rook are in double precision.

let number := 10;
let numberTwo := 0.453;
let numberThree := 45.034;
let another := 34 + 45 / 456 * 2; //Expressions are also supported
// Rook follows JavaScripts Precedence rules

Numbers contain a few methods:

Number Functions

Since unary operators are not supported yet, Numbers have a Negate property that returns a negated new number.

let negatedOne := 10.Negate; //-10
let negatedTwo := negatedOne.Negate; //10

let sqrt := 10.Sqrt; //Square root
let sqr := 10.Sqr; //Square
let exponential := 10.Exp; //Exponential
let absolute := 10.Abs; //Absolute
let cosine := 10.Cos; //Cosine
let sine := 10.Sin; //Sine
let power := 10.Power(2); //10 Power 2 => 100
let log := 10.Log(10); //Log base 10 of 10

Strings

Strings are textual data. " is used to surround string data. \ can be used to excape characters but special characters E.g \n \t and others are not supported yet.

let string := "Hello world!";

Strings contain a few methods:

Concatnation

**+** or Concat method can be used to concatnate strings.

let string := "Hello" + " world!";
//A + can be used to concatnate strings

let stringTwo := string.Concat("again");
let stringThree := "Another".Concat(" string");
//Using Concat method.

ToNumber property which converts a string to a Number.

let s := "200";
s.ToNumber; // Returns 200 as a number
"200".ToNumber; // is also valid

Booleans

A boolean is a simpe true/false value.

let trueValue := True;
let falseValue := False;

Booleans can also be computed. Example:

let bool := True || False;
let boolTwo := True && True || False;
//Etc

Note: Strings with "False" (without quotes), "Null" (without quotes) or empty strings are casted to False when using them as booleans, everything else is casted to True

let bool := "Test" || False; // Returns True

Numbers are not implicitly converted to Booleans yet. But if you wanted to use numbers, you could use numbers as follows:

let bool := 0 == 0 || False; // Returns True

let x := 12;
let isGreaterThanTen := x > 10; // This returns False

Null

Null in Rook is an equivalent to nothing.

let x: // Rook assigns Null to x implicitly
let y := Null; // Or you could explicitly assign Null

Lists

Lists in Rook are almost equivalent to Python lists. They are initialised with [] for empty lists. They can take any of Rook's basic types.

let list := []; // Initializes an empty list
let listTwo := ["string", Null, False, 23]; // Can accept any type

Lists contains a few methods:

Add

Used to add an item at the end of the list

let list := [];
list.Add(10); // [10]
list.Add(20); // [10, 20]
list.Add(30); // [10, 20, 30]
list.Add("end"); // [10, 20, 30, "end"]

list[0] := 45; // [45, 20, 30, "end"]

let x := list[3]; // x is now "end"

list.Length; //Returns the number of items on the list

Functions

Lets go through functions and function calls before if statements. There is a good reason. Trust me.
All functions in Rook are higher order functions. They can be passed as parameters and returned as return values. Functions are denoted by { and } so everything between those two curly brackets are considered within the function.

let f := {} // This is an empty function

All functions return a value. Empty functions return Null
There is no return statement in Rook. The value of the last statement is returned instead.

let here := { 10; } //Function here would returh 10
// And since every statement returns a value, even assignments..
let there := {
    let x := 10;
}
// Then the above function would also return 10;

Functions with arguments

If you are defining a function that expects parameters, you use :( [params] ) immedietly after { Example:

let Power := {:(num, pow)
    num.Pow(pow);
}
let x := Power(10, 2)
//Value x would be 100, thats 10 power 2

Rook supports nested functions, but inner functions are only accessible locally. Its impossible to call a function within another function while outside the parent scope unless the inner function is the return value. (Still debating whether to use . notation to access inner functions globally...)

Function calls

Function calls are similar to most programming languages

FunctionName(); // A function which does not accept any parameters
FunctionName(10, 30); // Calling a function that accepts 2 params
// Etc

Conditional Statement

If - then - else is the only conditional statement in Rook. The else part is optional. Remember every statement in Rook returns a value? Well, even an ifstatement is not an exception.

 //if condition then Expression  | Function call | function else Expression | Function call | Function
 if 10 > 20 then 10 else 20; 
 
 //Brackets on if condition is not a must
 if(10 > 20) then 10 else 20; // This is still valid
 
 if 20 <= 34 then f() else g() // f and g are imaginary functions

 if 10 == 20 then 400; // this evaluates to Null
  
 //Remember if statement returns a value, well...
 let x := if 40 > 20 then 400 else 200 + 34; //x => 300

A function definition is also valid after then or else

let n := if True then {
    10;
} else {
    200;
}
// n will evaluate to 10

For now, its not possible to use both function definition and an Expression on the same if statement. (Its a bug)

let s := if False then 10 else { 200; } // This will fail
let g := if False then 10 else 200; // This is also correct
let f := if False then { 10; } else { 200; } // This is correct 

Loops

Conventional loop statements like while for foreachare not supported in Rook. However, Recursion is fully supported.

For example, Printing 1 - 10 can be done as follows:

let Printer := {:(start, end)
    if start >= end then { 
        Null;
    else {
        Print(start);
        Printer(start + 1, end);
    }
}

//Then call printer
Printer(1, 10);

I am debating whether to add conventional loops, still undecided :)

Below is are a few simple algorithms that runs on Rook

/**
 * This function gets the age and returns the ticket
 */
let CalculateTicket := {:(age)
    let basePrice := 100;
    if age >= 18 then basePrice + 300 else basePrice + 100;
  }

/*
* This function calculates the age
* @params birthYear Number
* @return age Number
*/

let GetAge := {:(birthYear)
  2018 - birthYear;
}

Print("Welcome to IMAX movie theatre.");
Print("We would like a few of you details.");
let s := Read("Enter your birth year: ").ToNumber;
let age := GetAge(s);
let ticket := CalculateTicket(age);

let ans := "Your ticket is: ".Concat(ticket).Concat(". enjoy!");

Print(ans);
// This is a comment

let Printer := {:(list, index)
  Print(list[index]); 
  if index != list.Length - 1 then Printer(list, index + 1);
}

let Populate := {

  let items := [];
  let s := Read("Enter a number to add to a list(q to quit): ");
  if s == "q" then {
      if items.Length > 0 then {
        Print("Here are the contents of the list:");
        Printer(items, 0);
      } else {
        Print("The list has no items to display");
      }
  } else {
      items.Add(s.ToNumber);
      Populate();
  }
}

Populate();

This is STILL under construction