Table of Contents

1. About
2. Feature Showcase
3. Libraries
4. Todo

About

Pola is an interpreted object-oriented programming language written in Kotlin created for learning purposes. Examples can be found in the examples directory.

Feature Showcase

Note: Examples marked with a "*" assume that some libraries have been imported.

Comments

# This is a comment

Imports

import("io") # An instance of the class IO
import("array") # A reference to the class Arrays
val println = io.println # A reference to the function io.println

Math

var x = 10
x = x + 10 # 20
x = x - 10 # 10
x = x / 2 # 5
x = x * 2 # 10
x = x % 2 # 0
x = ++x # 1
x = --x # 0

Variables

var mutable = "This is mutable."
val immutable = "This is immutable."

Primitives

val num = 0
val bool = true

Objects *

val str = "string"
val arr = array(0, 1)

Control Flow

if(true) {
}

while(true) {
}

for(i = 0; i < 10; i = ++i) {
}

First-Class Functions *

# Num -> Boolean
fun isEven(value) {
    return value % 2 == 0
}

val num = 5
val isNumEven = isEven(x) # false

val numArray = array(1, 2, 3, 4)
val evenNumArray = numArray.filter(isEven) # [2.0, 4.0]

Anonymous Functions *

val x = array(0, 1, 2, 3) # [0.0, 1.0, 2.0, 3.0]
val xPlusOne = x.map(fun (value) {
    return ++value
}) # [1.0, 2.0, 3.0, 4.0]

Classes *

class Product {
    # (String, String, Num) -> Product
    init(name, brand, price) {
        this.name = name
        this.brand = brand
        this.price = price
    }
    
    # () -> String
    toString() {
        return "The " + this.name + " from " + this.brand + " costs $" + this.price + "."
    }
}

class MottsAppleSauce inherits Product {

    # () -> MottsAppleSauce
    init() {
        super.init("Applesauce", "Mott's", 7)
    }
}

val applesauce = MottsAppleSauce() # Instance of MottsAppleSauce
val coke = Product("Coke", "Coca Cola", 2) # Instance of Product

Libraries

IO

Name	Returns	Parameters	Arity	Comments
readln	string	n/a	0
print	string	textToPrint	infinite	Does not include a newline.
println	string	textToPrint	infinite	Includes a newline.
file	file	fileName	1	Does not perform any error checking.

Sys

Name	Returns	Parameters	Arity	Comments
exit	n/a	value	1

Array

Name	Returns	Parameters	Arity	Comments
get	any	index	2
set	array	index, newValue	3
remove	array	index	2
filter	array	filteringFunc	2	filteringFunc will be passed each item of the array and should return true for values to keep and false for values to discard.
foreach	n/a	applicationFunc	2	applicationFunc will be passed each item of the array and optionally the index of the item, returned values will be discarded.
map	array	applicationFunc	2	applicationFunc will be passed each item of the array and optionally the index of the item and should return a replacement value.

String

Name	Returns	Parameters	Arity	Comments
get	string	index	2
set	string	index, newValue	3
remove	string	index	2
filter	string	filteringFunc	2	filteringFunc will be passed each character of the string and should return true for values to keep and false for values to discard.
foreach	n/a	applicationFunc	2	applicationFunc will be passed each character of the string and optionally the index of the character, returned values will be discarded.
map	string	applicationFunc	2	applicationFunc will be passed each character of the string and optionally the index of the character and should return a replacement value.
replace	string	replacee, replacer	3	All occurrences of replacee in the string will be replaced with replacer.

File

Name	Returns	Parameters	Arity	Comments
read	string	n/a	1
isFile	bool	n/a	1
exists	bool	n/a	1
delete	bool	n/a	1	This will likely be changed to return the File instance.
create	bool	n/a	1	See above
write	bool	text	2	See above

Errors

Name	Returns	Parameters	Arity	Comments
try	The result of tryFunc or catchFunc	tryFunc, catchFunc	2	Catches all errors. catchFunc is called with the error message thrown during tryFunc.
throw	n/a	message	1	Throws an Error instance.

Todo

• Create a Javadoc
• Improve README documentation
• Remove primitives