Album source code is written like a playlist, in the form of a list of songs (instructions). Each song, when played (executed), does something different to the stack. Everything is case insensitive. The stack has an implementation-dependent size and stores signed 32-bit integers. When an empty stack is popped, or when an element is pushed onto a full stack, the playlist should terminate.
An Album source file begins with Playlist created by <name>, where the creator of the playlist (program) is declared. Every line before this line is a comment, and every line of this form after the first such line is also a comment.
After declaring the creator of the playlist, one of the following songs can be written on each line, otherwise it is considered a comment:
VORACITY, by Myth & Roid
Pushes the integer value of the user input, encoded in an implementation-dependent encoding that must be compatible with ASCII, onto the stack.
Do you hear the people sing? by Les Miserables
Pops the stack, output that element as an ASCII character. If the number is out of the range of ASCII, the behaviour is implementation-dependent.
Gasoline, by Halsey
Pops the stack, output that element as a number.
Man in the Mirror, by Michael Jackson
Pops the stack, pushes that element multiplied by 2.
The Right Path, by Thomas Greenberg
Pops the stack, pushes that element after an arithmetic right shift by 1.
Killer Queen, by Queen
Clears the stack.
Let It Go, by Idina Menzel
Pops the stack.
Dirty Deeds Done Dirt Cheap, by AC/DC
Pops the stack, then pushes that element twice.
Dear Maria, Count Me In, by All Time Low
Pops the stack twice, then pushes the sum of the elements.
Sink or Swim, by Tyrone Wells
Pops the stack twice, then pushes the bitwise OR of the elements.
Take it from me, by The Weepies
Pops the stack twice, then pushes the result of the second popped element minus the first popped element.
Hideaway, by The Weepies
Pops the stack twice, then pushes the bitwise AND of the elements.
Desperado, by The Eagles
Pops the stack twice, then pushes the bitwise exclusive OR of the elements.
I'm so Tired, by Lauv & Troye Sivan
Stops playing the playlist (terminates the program).
Zenzenzense, by RADWIMPS
Pops the stack twice, then pushes the first popped element, and the second popped element, effectively swapping the top two elements on the stack.
Roundabout, by YES
Removes the bottom element of the stack, then pushes it onto the stack.
Rolling in the Deep, by Adele
Pops the stack, adds it to the stack as the bottom element.
King Nothing, by Metallica
Pops the stack, if the popped element is 0, push 1, otherwise push 0.
LOSER, by Kenshi Yonezu
Pops the stack, if the popped element is less than 0, push 1, otherwise push 0.
Nothing Compares 2U, by Sinead O'Connor
Pops the stack, if the popped element is greater than 0, push 1, otherwise push 0.
Never Gonna Give You Up, by Rick Astley
This song always loops, hence creating an infinite loop.
<number> Bottles of Beer On The Wall
Pushes <number> onto the stack. <number> can only be non-negative, and less than 100, because 100 beers is too many beers. The wall can't possibly handle that.
<original song name>, by <playlist creator name>
This declares an original song (label) if <playlist creator name> is the same as the name in the playlist creator declaration, otherwise this is a comment.
Country Roads, Take Me <original song name>
Pops the stack, the playlist will start playing from the specified original song (jump to that label), if the popped element is not 0.
There are also songs that push specific numbers onto the stack:
| Song Name | Number Pushed |
|---|---|
| 50 Ways to Say Goodbye, by Train | 50 |
| Senbonzakura, by Kurousa-P | 1000 |
| I'm Gonna Be (500 Miles), by The Proclaimers | 500 |
Alternative spellings of all of these song names could be accepted depending on the implementation.
Each song name can have trailing and leading whitespace, and can optionally be ended with a semicolon, or a period.
The meaning of a line can be ambiguous. For example, the third line of:
Playlist created by Bob
Home, by Bob, by Bob
Country Roads, Take Me Home, by Bob
could be interpreted as declaring an original song named "Country Roads, Take Me Home", or it could be interpreted as the Country Roads song, with the <original song name> being "Home, by Bob". The second line is also problematic - this could be interpreted as an original song called "Home, by Bob", that is by Bob, or it could be parsed as "Home" by "Bob, by Bob". In the latter case though, since "Bob, by Bob" is not the playlist creator name, the line will just be a comment. To disambiguate this, the following rules apply,
- if a line can be interpreted as a song that is neither a Country Roads song nor an original song, it will be interpreted as that song, otherwise;
- if a line can be interpreted as a Country Roads song, it will be, otherwise;
- if a line can be interpreted as an original song, it will be, otherwise;
- the line is interpreted as a comment
An Album implementation is NOT required to terminate the playlist after the last song is played, so it is recommended to add the song "I'm So Tired, by Lauv & Troye Sivan" at the end of every playlist that isn't intended to play on loop forever.