Whitespace

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Whitespace with syntax highlighting

Whitespace, designed in 2003 by Edwin Brady and Chris Morris, is an imperative, stack-based, esoteric programming language that uses only whitespace characters—space, tab, and linefeed—as syntax. All other characters are ignored. Whitespace got a brief moment of fame when it was posted on Slashdot on April 1st, 2003. Most people took it as an April Fool's joke, while it wasn't.

This page uses [Space], [Tab], and [LF] for Space (ASCII 32), Tab (ASCII 9), and Line Feed (ASCII 10) respectively.

Commands

IMP

There are different types of commands in Whitespace, and they all have different Instruction Modification Parameters (IMP), which can be thought of as the category a command falls in. Every command starts with an IMP, followed by the remainder of the command, and followed by parameters, if necessary.

IMP Command
[Tab][LF] I/O
[Space] Stack Manipulation
[Tab][Space] Arithmetic
[LF] Flow control
[Tab][Tab] Heap access

Numbers

Numbers start with a sign ([Space] for positive or [Tab] for negative), then have a sequence of [Space] (0) and [Tab] (1) representing the number in binary, and end with [LF].

I/O

Commands Parameters Meaning
[Tab][Space] - Pop a heap address from the stack, read a character as ASCII, and store that character to that heap address
[Tab][Tab] - Pop a heap address from the stack, read a number, and store that number to that heap address
[Space][Space] - Pop a number from the stack and output it as an ASCII character
[Space][Tab] - Pop a number from the stack and output it

The general pattern for the IO instructions is that the first character is [Tab] when an instruction is for input, and [Space] when it's for output. The second character is then [Space] for a character, and [Tab] for a number.

Stack manipulation

Commands Parameters Meaning
[Space] Number Push a number to the stack
[LF][Space] - Duplicate the top item on the stack
[LF][Tab] - Swap the top two items on the stack
[LF][LF] - Discard the top item on the stack
[Tab][Space] Number Copy the nth item on the stack (given by the argument) onto the top of the stack (v0.3)
[Tab][LF] Number Slide n items off the stack, keeping the top item (v0.3)

Arithmetic

Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first element pushed is considered to be left of the operator.

Command Parameters Meaning
[Space][Space] - Addition
[Space][Tab] - Subtraction
[Space][LF] - Multiplication
[Tab][Space] - Integer Division
[Tab][Tab] - Modulo

Flow Control

Commands Parameters Meaning
[Space][Space] Label Mark a location in the program
[Space][Tab] Label Call a subroutine
[Space][LF] Label Jump unconditionally to a label
[Tab][Space] Label Jump to a label if the top of the stack is zero
[Tab][Tab] Label Jump to a label if the top of the stack is negative
[Tab][LF] - End a subroutine and transfer control back to the caller
[LF][LF] - Ends the program

Labels are a sequence of [Space] and [Tab], ended by [LF].

Heap Access

Heap access commands look at the stack to find the address of the items to be stored or retrieved. To store a number, the address and value must be pushed in that order, then the store command must be run. To retrieve a number, the address must be pushed and the retrieve command must be run after; this will push the value at the given address to the stack.

Command Parameters Meaning
[Space] - Store
[Tab] - Retrieve

Examples

Cat program

[LF][Space][Space][Space]
[LF][Space][Space][Space][Tab]
[LF][Tab]
[LF][Tab][Space][Space][Space][Space][Tab]
[LF][Tab][Tab][Tab][Tab]
[LF][Space][Space][Space][Space][Space][Tab]
[LF][Tab][Tab][Tab]
[LF][Tab][Space][Tab]
[LF]
[LF][Space]
[LF][Space]
[LF]
[LF][Space][Space][Tab]
[LF]
[LF]
[LF]
[LF]

Hello, world!

Hello,[Space]world![Space][Space][Tab][Space][Space][Tab][Space][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Space][Tab][Space][Tab][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Tab][Tab][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Tab][Tab][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Tab][Tab][Tab][Tab][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Space][Tab][Tab][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Space][Space][Space][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Tab][Space][Tab][Tab][Tab][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Tab][Tab][Tab][Tab][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Tab][Space][Space][Tab][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Tab][Tab][Space][Space][LF]
[Tab][LF][Space][Space]
[Space][Space][Space][Tab][Tab][Space][Space][Tab][Space][Space][LF]
[Tab][LF][Space][Space]
[LF][LF][LF]

Truth-machine

[Space][Space][Space][LF]
[Space][LF][Space]
[Tab][LF][Tab][Tab]
[Tab][Tab][Tab]
[LF][Tab][Space][Space][LF]
[LF][Space][Space][Tab][LF]
[Space][Space][Space][Tab][LF]
[Tab][LF][Space][Tab]
[LF][Space][LF][Tab][LF]
[LF][Space][Space][Space][LF]
[Space][Space][Space][LF]
[Tab][LF][Space][Tab]
[LF][LF][LF]

See also

External resources

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