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Schemy Lisp En DOS
SLED (Schemy Lisp en DOS) is a purely symbolic LISP (LISt
Processor) with functionality (largely) inspired by Scheme. Originally
derived from the fantastic Kilo LISP, but reduced by
some features (such as macros), and enhanced with others, SLED can be classified
as an Ur-Lisp and runs on a DOS (Disk Operating System) such as
FreeDOS or MS-DOS, as well as on DOS-emulators like
DOSBox, DOSBox-X, or
DOSBox-Staging.
For an overview of provided symbols, special forms, builtin functions, and
standard library see the index.
Get SLED:
There are two fundamental data types: Pairs and Atoms (not-pairs). Atoms
come in three variants: Symbols, Closures (functions), and some
Special Symbols.
Symbols are unique names and consist of any combination of maximum 16 of
the following characters:
Additionally, any printable ASCII character can be part of a symbol when
prefixed with the escape character \ (backslash), with the exception of (,
), ', and $.
Furthermore, uppercase letters are accepted but converted to lowercase unless
the character is escaped.
There are some predefined special symbols managed by SLED, for example nil
which means "empty list". See the index for details.
A quote means "do not evaluate". Via the quote special form a symbol is
registered:
For convenience the ' short form syntax may be used:
Essentially quoting declares something as data instead of code.
Pairs consist of a head and a tail, each
holding either an atom or another pair. A pair can be
created as data using the . (dot):