The Cub Programming Language
by Louis D'hauwe
Table of Contents
Intro
Cub is a scripting language with a lightweight syntax. It was inspired by Swift. Cub is easy to learn and fast to write. This document guides you through all the language features of Cub and is suitable for people with little programming experience.
A Cub script can be as simple as:
print("Hello world")
Features
Variables
A variable can be declared in the following way:
myVariable = 42
A variable can change its value at any time:
myVariable = 42
myVariable = 10
Values are copied on assignment:
a = 10
b = a
a += 1
// a is now 11
// b is still 10
Types
Cub is a dynamic language. This means that variables don't have a fixed type. A variable can change its type at any time:
myVariable = 42
myVariable = "awesome!" // this overrides the value from the previous line
Number
All numbers in Cub are floating point.
myNumber = 3.14
Numbers can be negative:
a = -10
The following operators are supported:
a = 1 + 2 // 3
b = 2 - 1 // 1
c = 2 * 2 // 4
d = 1 / 2 // 0.5
e = 2 ^ 3 // = 2 * 2 * 2 = 8
Boolean
A boolean value can be obtained using a literal:
isAwesome = true
doEvil = false
as well as using a condition:
myNumber = 10
isLargeNumber = myNumber > 5 // evaluates to true
Cub supports the following comparison operators:
myNumber = 10
isLargerThan10 = myNumber > 10
isLargerThanOrEqual10 = myNumber >= 10
isSmallThan10 = myNumber < 10
isSmallThanOrEqual10 = myNumber <= 10
is10 = myNumber == 10
isNot10 = myNumber != 10
Cub supports three bitwise operators:
- The and operator (
&&) results to true if both boolean values are true:
and = true && false // equals false
and = true && true // equals true
This is very useful when combined with variables and statements:
isDragon = true
isGreen = true
if isDragon && isGreen {
// A green dragon
}
- The or operator (
||) results to true if at least one of the boolean values is true:
isDragon = true
isGreen = false
if isDragon || isGreen {
// is a dragon, or is green, or both
}
- The not operator (
!) negates a boolean value:
myNumber = 10
isLargeNumber = myNumber > 5 // evaluates to true
isSmallNumber = !isLargeNumber // evaluates to false
String
Strings are defined using quotes:
message = "Hello world!"
Strings can be concatenated:
name = "Steve"
message = "Hello " + name // "Hello Steve"
Array
An array is defined using square brackets:
favoriteNumbers = [2, 4, 8]
Arrays can contain different value types:
thingsILove = [3.14, "pie", true]
Arrays can also contain other arrays:
square = [[1, 2], [3, 4]]
Variables can be used in arrays like any other value:
favoriteColor = "red"
favorites = [favoriteColor, 3.14]
A value can be added to an array using the add operator:
thingsILove = [3.14, "pie"]
thingsILove += "Cub" // thingsILove now equals [3.14, "pie", "Cub"]
Adding two arrays results in one array:
thingsILove = [3.14, "pie"]
thingsILove += ["Cub", "OpenTerm"]
// thingsILove now equals [3.14, "pie", "Cub", "OpenTerm"]
A value can also be added to the front of an array:
favoriteColor = "red"
thingsILove = [3.14, "pie"]
thingsILove = favoriteColor + thingsILove
// thingsILove now equals ["red", 3.14, "pie"]
Accessing a value from an array is possible using a subscript:
thingsILove = [3.14, "pie"]
firstThingILove = thingsILove[0] // arrays start counting from 0
Trying to access a value at an invalid index results in a runtime crash:
thingsILove = [3.14, "pie"]
thirdThingILove = thingsILove[2] // script will abort
You can loop over all the values in an array:
numbers = [1, 2, 3]
for number in numbers {
// do something
}
Struct
A struct is a special value that contains other values. You define a struct like this:
struct Point {
x, y
}
You can create an instance of a struct by using the struct's name:
myPoint = Point(2, 4)
You access a value in a struct using the name of that member:
myPoint = Point(2, 4)
x = myPoint.x
Structs can contain any value, including other structs:
struct Point {
x, y
}
struct Size {
width, height
}
struct Rect {
origin, size
}
rect = Rect(Point(0, 0), Size(2, 4))
The value of a struct can be edited by assigning to one of its members:
myPoint = Point(2, 4)
myPoint.x = 3
// myPoint now equals (3, 4)
Conditional statements
Cub supports if statements:
myNumber = 42
if myNumber > 10 {
// do something
}
If statements can be followed by an else statement:
myNumber = 42
if myNumber > 40 {
// do something
} else {
// do something else
}
If statements can also be followed by an else-if statement:
myNumber = 42
if myNumber > 40 {
// do something
} else if myNumber > 30 {
// do something else
}
An if statement can have an unlimited number of subsequent else-if statement:
myNumber = 42
if myNumber > 40 {
// do something
} else if myNumber > 30 {
// do something else
} else if myNumber > 20 {
// do something else
} else if myNumber > 10 {
// do something else
}
An else statement, if present, must be the last statement in an if statement:
myNumber = 42
if myNumber > 40 {
// do something
} else if myNumber > 30 {
// do something else
} else if myNumber > 20 {
// do something else
} else if myNumber > 10 {
// do something else
} else {
// fallback
}
Loops
Since Cub is a scripting language, loops are an essential part.
For loop
A for loop executes its body using an iterator variable:
numbers = []
for i = 1, i<=10, i += 1 {
numbers += i
}
// numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
While loop
A while loop executes its body until its condition is false:
a = 10
i = 0
while a > 2 {
a -= 2
i += 1
}
// a now equals 2
// i now equals 4
Do times loop
A do times loop executes its body a fixed number of times:
do 10 times {
// this will be executed 10 times
}
You can also pass a variable:
n = 10
do n times {
// this will be executed n times
}
Repeat while loop
A repeat while loop executes its body at least once, until its condition is false:
i = 10
repeat {
i *= 2
} while i < 5
// i now equals 20
Continue
You can use a continue statement to skip an iteration in a loop:
numbers = []
for i = 1, i<=10, i += 1 {
if i == 2 {
continue
}
numbers += i
}
// numbers = [1, 3, 4, 5, 6, 7, 8, 9, 10]
Break
You can use a break statement to exit a loop early:
numbers = []
for i = 1, i<=10, i += 1 {
if i == 2 {
break
}
numbers += i
}
// numbers = [1]
Functions
Functions provide reusable pieces of code:
func doSomething() {
// do something
}
A function can be called using its name:
doSomething()
A function can return a value:
func getNumber() returns {
return 10
}
A function can take arguments:
func sum(a, b) returns {
return a + b
}
total = sum(2, 4) // total = 6
Unicode support
Cub supports all unicode characters, including emoticons. You can even use emoticons as variable and function names:
func ∑(a, b) returns {
return a + b
}
😀 = ∑(2, 4) // 😀 = 6