Whitespace is formally specified by its implementation, not by a language reference. This document attempts to fill in gaps from the tutorial with details from testing the reference interpreter and to compare various implementations.
The only tokens in the Whitespace language are space (U+0020), tab (U+0009), and line feed (U+000A), represented hereafter as S, T, and L, respectively. All other characters are considered comments and must be ignored.
S, T, LS, T, NS, T, line feed U+000AA, B, CAll values in Whitespace are arbitrary-precision integers.
Instructions are grouped with a shared prefix, called the “instruction modification parameter” in the tutorial.
| Prefix | Group |
|---|---|
| S | Stack manipulation |
| TS | Arithmetic |
| TT | Heap access |
| L | Control flow |
| TL | I/O |
| Mnemonic | Syntax | Arg | Stack | Heap | Description |
|---|---|---|---|---|---|
| push | SS | n | – n | Push the number onto the stack | |
| dup | SLS | x – x x | Duplicate the top item on the stack | ||
| copy | STS | n | a0 .. an – a0 .. an a0 | Copy the nth item on the stack (given by the argument) onto the top of the stack | |
| swap | SLT | x y – y x | Swap the top two items on the stack | ||
| drop | SLL | x – | Discard the top item on the stack | ||
| slide | STL | n | a0 .. an – an | Slide n items off the stack, keeping the top item | |
| add | TSSS | x y – x+y | Addition | ||
| sub | TSST | x y – x-y | Subtraction | ||
| mul | TSSL | x y – x*y | Multiplication | ||
| div | TSTS | x y – x/y | Integer Division | ||
| mod | TSTT | x y – x%y | Modulo | ||
| store | TTS | addr val – | addr <- val | Store | |
| retrieve | TTT | addr – *addr | Retrieve | ||
| label | LSS | l | – | Mark a location in the program | |
| call | LST | l | – | Call a subroutine | |
| jmp | LSL | l | – | Jump unconditionally to a label | |
| jz | LTS | l | cond – | Jump to a label if the top of the stack is zero | |
| jn | LTT | l | cond – | Jump to a label if the top of the stack is negative | |
| ret | LTL | – | End a subroutine and transfer control back to the caller | ||
| end | LLL | – | End the program | ||
| printc | TLSS | char – | Output the character at the top of the stack | ||
| printi | TLST | int – | Output the number at the top of the stack | ||
| readc | TLTS | addr – | addr <- char | Read a character and place it in the location given by the top of the stack | |
| readi | TLTT | addr – | addr <- int | Read a number and place it in the location given by the top of the stack |
The instruction prefix encoding is not self-synchronizing.
The mnemonics used here follow the Whitelips/Nebula convention and are non-normative. Whitespace assembly dialects vary widely between implementations and are out of scope of this document.
Some implementations define non-standard instructions.