Awesome

Whitespace

Whitespace is a language invented in 2003 by two students at the University of St. Andrews in Scotland. It is unique in that it has only three valid characters: space, tab, and newline. All instructions are formed by different patterns of those characters.

The original site describing the language is down; however, it is preserved in the wayback machine here.

Interestingly, Whitespace has been bootstrapped; there is a Whitespace interpreter written in Whitespace.

The Compiler

This is a Just-In-Time compiler/interpreter for Whitespace. It interprets a program written in Whitespace, parses it, and generates and runs x86-64 machine code which is equivalent to the input program. Unfortunately we do violate the specification a little for simplicity's sake:

• Integers are not arbitrary-width, and are instead always 64 bits wide.
• The modulo operator produces undefined results when either operand is negative.
• When outputting characters, only ASCII values are supported. The encoding is not defined in the spec.
• When reading characters, it is required for the user to press enter between each character. This is for simplicity - it would require the ncurses library to read characters without requiring an enter press due to the way stdin is buffered. This may be fixed later.

Motivation

Because it is so simple, Whitespace is easy to parse. One reason I wrote this is to learn the parser combinator library nom. My biggest other goal was to become more familar with x86-64 assembly programming and the Rust language, which the compiler is written in.