Tommy used to work on the docs.

The Rockstar Language Specification

Rockstar is intended to give the programmer an unprecedented degree of poetic license when it comes to the composition and structure of their programs.

File format

Rockstar programs are UTF-8 files with the .rock file extension. (Given that for everything included in the current Rockstar specification, UTF-8 is indistinguishable from 7-bit ASCII, that’s a fancy way of saying they’re plain text files.)


The use of comments in Rockstar programs is strongly discouraged. This is rock’n’roll; it’s up to the audience to find their own meaning. If you absolutely insist on commenting your Rockstar programs, comments should be contained in parentheses (). Yes, this means you can’t use brackets in arithmetic expressions and may need to decompose complex expressions into multiple evaluations and assignments.

Rockstar developers are not into that whole brevity thing.

(Initialise Tommy = 1337)
Tommy was a big bad brother. 


Rockstar supports three kinds of variable names.

Simple variables are valid identifiers that are not language keywords. A simple variable name must contain only letters, and cannot contain spaces. Note that Rockstar does not allow numbers or underscores in variable names - remember the golden rule of Rockstar syntax: if you can’t sing it, you can’t have it. Simple variables are case-insensitive.

Variable is 1
Tommy is a rockstar
X is 2
Y is 3
Put x plus y into result

Common variables consist of one of the keywords a, an, the, my, your or our followed by whitespace and a unique variable name, which must contain only lowercase ASCII letters a-z. The keyword is part of the variable name, so a boy is a different variable from the boy. Common variables are case-insensitive.

My variable is 5
Your variable is 4

Put my variable plus your variable into the total
Shout the total

Proper variables are multi-word proper nouns - words that aren’t language keywords, each starting with an uppercase letter, separated by spaces. (Single-word variables are always simple variables.) Whilst some developers may use this feature to create variables with names like Customer ID, Tax Rate or Distance In KM, we recommend you favour idiomatic variable names such as Doctor Feelgood, Mister Crowley, Tom Sawyer, and Billie Jean.

(Although not strictly idiomatic, Eleanor Rigby, Peggy Sue, Black Betty, and Johnny B Goode would also all be valid variable names in Rockstar.)

As in Ruby, Python and VBScript, variables are dynamically typed and you don’t need to declare variables before use.

If a variable is defined outside of a function, it is in global scope. Global scope variables are available everywhere below their first initialization. If a variable is defined inside of a function, it is in local scope. Local scope variables are available from their initialization until the end of the function they are defined in.

While within a function, if you write to a variable that has been defined in global scope, you write to that variable; you do not define a new local variable.

A note on case sensitivity in Rockstar

Rockstar keywords and variable names are all case-insensitive, with the exception of proper variables. Proper variables are case-insensitive apart from the first letter of each word, which must be a capital letter.


The keywords it, he, she, him, her, they, them, ze, hir, zie, zir, xe, xem, ve, and ver refer to the last named variable determined by parsing order.

(Please don’t file issues pointing out that 80s rockers were a bunch of misogynists and gender-inclusive pronouns aren’t really idiomatic. You’re right, we know, and we’ve all learned a lot since then. Besides, Look What The Cat Dragged In was recorded by four cishet guys who spent more money on lipgloss and hairspray than they did on studio time, and it’s an absolute classic.)


Rockstar uses a similar type system to that defined by the ECMAScript type system, except undefined doesn’t sound very rock’n’roll so we use mysterious instead.

Functions and function identifiers are not strictly part of the type system in Rockstar 1.0.


Rockstar supports JavaScript-style arrays. Arrays are zero-based, and dynamically allocated when values are assigned using numeric indexes.

Let the array at 0 be "zero"
Let the array at 1 be "one"
Let the array at 255 be "big"
Shout the array at 0
Shout the array at 255

Returning an array in a scalar context will return the current length of the array:

Let my array at 255 be "some value"
Shout my array (will print the value 256)

Rockstar also supports non-numeric array keys, so it is valid to say:

let my array at "some_key" be "some_value"
Shout my array at "some_key"

You can mix string and numeric keys within the same array. The array length property ignores any non-numeric keys:

Let my array at "some_key" be "some_value"
Shout my array (will print 0, since there are no numeric indexes)
Let my array at 7 be "some other value"
Shout my array (will now print 8, since assigning my array at 7 modifies the array length)

You can also use array index syntax to read (but not write) specific characters from a string

Let my string be "abcdefg"
Shout my string at 0 (will print "a")
Shout my string at 1 (will print "b")
Let the character be my string at 2

Queue operations

Rockstar arrays can also be created and manipulated by the queue operations rock and roll. (The aliases push and pop are supported for Rockstar developers who are into 80s dance music.)

Pushing elements onto an array

To create a new empty array, rock the name of the array:

Rock the array (the array is now [])

To push an element onto the end of an array:

Rock the array with the element

This supports list expressions, so you can push multiple elements onto the end of an array:

Rock ints with 1, 2, 3 (ints is now [1, 2, 3])
Rock the array with the first, the second, and the third

Remember the with keyword is context-sensitive, so in this example:

Rock ints with 1, 2 with 3, 4, 5
          ^         ^
          |         +-- this 'with' is the binary addition operator
          +------------ this 'with' is part of the array push syntax
(ints is now [ 1, 5, 4, 5 ])

Rockstar supports a special syntax for pushing poetic literals onto a queue:

Rock the array like the poetic literal (the array is now [ 367 ])
Rock the array like a wolf (the array is now [ 367, 14 ])

This syntax is very useful for initialising strings without using string literals - see below. It also means that the following line is valid Rockstar:

Rock you like a hurricane (you is now [ 19 ])

Popping elements from an array

The roll keyword will remove the first element from an array and return the element that was removed.

Rock ints with 1, 2, 3
Roll ints (returns 1; ints is now [ 2, 3 ])
Roll ints (returns 2; ints is now [ 3 ])
Roll ints (returns 3; ints is now [] )
Roll ints (returns mysterious; ints is now [])

roll can be used in assignments:

Rock ints with 1, 2, 3
Let the first be roll ints
Let the second be roll ints
Let the third be roll ints
Shout the first (outputs 1)
Shout the second (outputs 2)
Shout the third (outputs 3)

Rockstar also supports a special roll x into y syntax for removing the first element from an array and assigning it to a variable:

Rock the list with 4, 5, 6
Roll the list into foo
Roll the list into bar
Roll the list into baz
Shout foo (will output 4)
Shout bar (will output 5)
Shout baz (will output 6)

Splitting strings and type conversions

A note about mutations

Some operations in Rockstar will either act in-place, modifying the variable passed to them, or will leave the source variable unmodified and place their output into a target variable. These operations are known as mutation operations, and they all have the following syntax:

Note that in-place mutations are only valid where the first argument is a variable:

Splitting Strings

To split a string in Rockstar, use the cut mutation (aliases split and shatter)

String splitting can either operate in-place, or place results into an output variable. You can specify an optional delimiter; if no delimiter is provided, the string is split into a character array.

Split "a,b,c" into the array (the array is ["a", ",", "b", ",", "c"])
Split "a,b,c" into the array with "," (the array is ["a", "b", "c"])
Split my string (my string will split in-place to an array of characters)
Split my string with x (split my string in-place using the current value of x as a delimiter)

Cut my life into pieces 
  (split my life, put the resulting array in pieces)

Cut your cake with my knife
  (modify your cake in-place, by splitting it using my knife as a delimiter)

Shatter my heart into pieces with your lies
   (Split my heart, using your lies as a delimiter, and put the result into pieces)

In-place string splitting is only valid when the first argument is a variable; the following would be invalid (because where would the result actually go?)

Split "a,b,c,d,e" with "," (NOT VALID - nowhere to place the output)
Split "a,b,c,d,e" into tokens with "," (valid - tokens now contains ["a","b","c","d","e"])

Joining Arrays

To join an array in Rockstar, use the join mutation, or the alias unite

Let the string be "abcde"
Split the string into tokens
Join tokens with ";"
    (the tokens now contains "a;b;c;d;e")

The input says hey now hey now now
Split the input into words with " "
Unite words into the output with "! "
    (the output now contains "hey! now! hey! now! now!")

Parsing numbers and character codes

Use the cast mutation (alias burn) to parse strings into numbers, or to convert numbers into their corresponding Unicode characters.

Let X be "123.45"
Cast X
    (X now contains the numeric value 123.45)
Let X be "ff"
Cast X with 16
    (X now contains the numeric value 255 - OxFF)
Cast "12345" into result
    (result now contains the number 12345)
Cast "aa" into result with 16
    (result now contains the number 170 - 0xAA)

Cast 65 into result
    (result now contains the string "A" - ASCII code 65)

Cast 1046 into result
    (result now contains the Cyrillic letter "Ж" - Unicode code point 1046)


The results of comparisons often rely on a concept called ‘truthiness’. If the value is truthy, it will be implicitly converted to true. If it is falsy, it will be implicitly converted to false.

Constants vs Keywords

Words that are used to construct a literal of a certain type are referred to as constants and words that are used to construct various syntax constructs are referred to as keywords

Constant Aliases
mysterious -
null nothing, nowhere, nobody, gone
true right, yes, ok
false wrong, no, lies
empty silent, silence

Literals and Assignment

String literals in Rockstar use double quotes.

Numeric literals in Rockstar are written as decimal numbers

Assignment is done using either put <expression> into <variable> or let <variable> be <expression>:

The keyword in is an alias for into.

Single Quotes

Given Rockstar’s intriguing ancestral mixture of computer programming, creative English and idiomatic rock’n’roll, the single quote character presents all sorts of challenges.

Most programming languages use the single quote for quoting literal strings - 'like this'. English, when written using the basic ASCII character set, often uses the single quote to stand in for the apostrophe to denote contractions or possessives - you're, she's, he's, shouldn't, rock'n'roll. Rock’n’roll uses the apostrophe apparently at random - sweet child o' mine, ain't talkin' 'bout love, guns n' roses.

Given three such dramatically different influences, here’s how Rockstar interprets single quotes.

  1. The sequence 's or 're appearing at the end of a word is equivalent to ` is`, except when used in poetic literals.

    • This allows Janie's got a gun (initialises Janie with the value 313) and Union's been on strike (initialises Union with the value 426) as valid variable declarations. We're here to see the show initialises We with the value 42334.
    • You can also use 's and 're in comparisons: If Janie's gone tests whether Janie is null.
  2. All other single quotes are then ignored. ain't is equivalent to aint, wakin' has five letters, and ''''' is equal to the empty string. This means you can use single quotes freely throughout your program to punctuate, adjust word lengths and generally channel the spirit of rock’n’roll without worrying about compiler errors.

The fire's burning Tommy's feet initialises the fire with the value 764.

Increment and Decrement

Increment and decrement are supported by the Build {variable} up and Knock {variable} down statements. Adding more than one up or down in the statement will increment or decrement the same amount of times as you have ups or downs in the statement. There may be a comma between each up and down.


Rockstar supports the infix arithmetic operators +, -, * and /. The language includes aliases for each operator so you can write lyrically pleasing expressions.

Operator Operation Aliases
+ addition plus, with .
- subtraction minus, without
* multiplication times, of
/ division over, between

The alias by has been explicitly rejected because of disagreements between the colloquial English ten by four (i.e. 10*4 = 40) and ten (divided) by four (i.e. 10/4 = 2.5)


Compound Assignment Operators

As in many C-style languages, Rockstar supports compound assignment operators, providing a terser syntax for storing the result of an operation. This is done using the let keyword.

Arithmetic Rounding

Rounding in Rockstar is performed by the turn keyword. Turn up will round up (i.e. towards positive infinity), to the nearest integer; turn down will round down (towards negative infinity) to the nearest integer, and turn round will round to the nearest integer. Bonnie Tyler enthusiasts will be pleased to note that Rockstar accepts turn around as a valid alias.

Turn operations act in-place: they modify the variable directly, and will return the rounded value.

X is 1.2
Turn up X
Shout X (will print 2)

X is 1.2
Turn down X
Shout X (will print 1)

The radio's playing. The night has just begun. 
 (initialises the radio with 7.35345)
Turn up the radio
Say the radio (will print 8)

Rounding supports variable pronouns, so you can write phrases like:

My heart is on fire. Aflame with desire.
Turn it up.
Shout it.

which will print the value 25 (obviously).

List Arithmetic

Rockstar operators support a list of expressions on the right-hand side of the operator. (Imagine explaining in English that, say, “the restaurant bill is the food, plus the drinks, the service, and the tax” - same idea.)

You can combine list arithmetic with compound assignment, as with this example:

The wolf is hungry, out on the street (initialise the_wolf = 63236)
Fear is the mind killer (fear = 346)
Fury is the demon child (fury = 355)
Hate is the only truth (hate = 345)
Let the wolf be without fear, fury, and hate (the_wolf = the_wolf - 346 - 355 - 345) 
Shout the wolf (output 62190)

List arithmetic is only possible where the result type supports further operations.

Poetic Literals

Rockstar also supports a unique language feature known as poetic literals. Inspired by the here-document syntax supported by many scripting languages, poetic literals allow the programmer to simultaneously initialize a variable and express their innermost angst.

Poetic Constant Literals

A poetic constant literal is a single line consisting of a variable name, the is keyword, or the aliases are, was or were, and a constant signifying the value the variable will be set to.

Poetic String Literals

A poetic string literal assignment starts with a variable name, followed by one of the keywords say, says or said followed by a single space. The rest of the line up to the \n terminator is treated as an unquoted string literal.

Poetic Number Literals

A poetic number literal begins with a variable name, followed by the keyword is, or the aliases are, was or were. As long as the next symbol is not a Literal Word, the rest of the line is treated as a decimal number in which the values of consecutive digits are given by the lengths of the subsequent barewords, up until the end of the line. To allow the digit zero, and to compensate for a lack of suitably rock’n’roll 1- and 2-letter words, word lengths are parsed modulo 10. A period (.) character denotes a decimal place. Other than the first period, any non-alphabetical characters are ignored.


Similar to the single-equals operator in Visual Basic and some scripting languages, the is keyword in Rockstar is interpreted differently depending whether it appears as part of a statement or as part of an expression. isn't is the logical negation of the is keyword.

Comparison in Rockstar can only be done within an expression.

Comparison can also be done with any alias of is:

The keyword ain't (which is reduced to aint by Rockstar) is an alias for isn't. This usage runs contrary to idiomatic English, where “Tommy isn’t anybody”, “Tommy ain’t nobody” and “Tommy ain’t not nobody” somehow mean exactly the same thing.

aren't, wasn't, and weren't are also aliases for isn't.

Rockstar also supports the following comparison syntax:

Logical Operations

Rockstar has 4 different logical operators that first convert their operand(s) to a boolean by truthiness.

All logical operators are short circuiting. This means if evaluating the first argument to the operator guarantees a result, the other argument is not evaluated. false and 1 over 0 is false and does not produce an error for dividing by zero.


Use the Listen keyword to read one line of input from STDIN. Use Listen to to capture the input into a named variable.

Use the Say keyword to write the value of a variable to STDOUT.

Rockstar defines Shout, Whisper and Scream as aliases for Say

The following examples all use c style syntax for explaining what things do.

Types Continued

Operator Precedence

The higher, the tighter the binding. This is the precedence we generally expect from our math.

  1. Function Call (greedy arguments)
  2. Logical NOT (right-associative)
  3. Multiplication and Division (left-associative)
  4. Addition and Subtraction (left-associative)
  5. Comparison operators (left-associative)
  6. and, or, and nor (left-associative)

Binary Comparison

Equality comparisons (is, ain't, is not) are allowed between types if they are the same type or they can be compared by the rules below. Two arrays are equal if their elements are equal.

Ordering comparisons (is higher than, is lower than, is as high as, and is as low as) are only allowed if the operands are both Numbers or both Strings or they are converted to such an arrangement according to the rules below. Numbers are compared as expected. Strings are compared lexicographically.


Increment and Decrement Operators

Binary Operators

Conversions other than those listed are errors.

Flow Control and Block Syntax


Conditional expressions start with the If keyword, followed by an expression. If the expression evaluates to true, then the subsequent code block is executed. Optionally, an Else block can be written after an If block. The code block following the Else keyword would be executed if the If expression evaluated to false.

For the purpose of conditional expressions, 0, mysterious, null, false, and the empty string all evaluate to false, and everything else to true.


Similar to the If statement, a loop is denoted by the While or Until keyword, which will cause the subsequent code block to be executed repeatedly whilst the expression is satisfied:

Tommy was a dancer
While Tommy ain't nothing,
Knock Tommy down

That’ll initialize Tommy with the value 16 (using the poetic number literal syntax) and then loop, decrementing Tommy by 1 each time until Tommy equals zero (i.e ain't nothing returns false).

The break and continue statements work as they do in most block-based languages. Rockstar defines Break it down as an alias for break and Take it to the top as an alias for continue


A block in Rockstar starts with an If, Else, While or Until statement, and is terminated by a blank line or the end-of-file. EOF ends all open code blocks

Tommy was a dancer
While Tommy ain't nothing
Shout it
Knock it down


Functions are declared with a variable name followed by the takes keyword (alias wants) and a list of arguments separated by one of the following: and , & , and 'n'

The function body is a list of statements with no separating blank lines. A blank line denotes the end of a function body. Functions in Rockstar always have a return value, specified by the return keyword and its aliases give and send. For historical reasons, give back is also supported as an alias for return, and the return statement can be followed by the keyword back (which has no effect but can make code more lyrical).

(This function adds 9 to its input and returns the result)
Polly wants a cracker
Cheese is delicious
Put a cracker with cheese into your mouth
Give it back

Functions are called using the ‘taking’ keyword and must have at least one argument. Multiple arguments are separated with one of the following: , & , and 'n'.

Arguments may be any valid expression, including literals, arithmetic expressions and function calls.


Here’s FizzBuzz in minimalist Rockstar, with block scope indented for clarity:

Modulus takes Number and Divisor
While Number is as high as Divisor
Put Number minus Divisor into Number
    (blank line ending While block)
Give back Number
    (blank line ending function declaration)
Limit is 100
Counter is 0
Fizz is 3
Buzz is 5
Until Counter is Limit
Build Counter up
If Modulus taking Counter, Fizz is 0 and Modulus taking Counter, Buzz is 0
Say "FizzBuzz!"
    (blank line ending 'If' Block)
If Modulus taking Counter and Fizz is 0
Say "Fizz!"
    (blank line ending 'If' Block)	
If Modulus taking Counter and Buzz is 0
Say "Buzz!"
    (blank line ending 'If' Block)
Say Counter (Note that the EOF terminates the `Until` block.)

And here’s the same thing in idiomatic Rockstar, using poetic literals and no indentation

Midnight takes your heart and your soul
While your heart is as high as your soul
Put your heart without your soul into your heart

Give back your heart

Desire is a lovestruck ladykiller
My world is nothing 
Fire is ice
Hate is water
Until my world is Desire,
Build my world up
If Midnight taking my world, Fire is nothing and Midnight taking my world, Hate is nothing
Shout "FizzBuzz!"
Take it to the top

If Midnight taking my world, Fire is nothing
Shout "Fizz!"
Take it to the top

If Midnight taking my world, Hate is nothing
Say "Buzz!"
Take it to the top

Whisper my world