Internals

This page very much under construction.

gherkin doesn't compile anything, but it does read strings into Lisp types.

Lisp types are represented by pointers which are bash strings of the following format: "${tag_marker}nnnddd..."

• $tag_marker is itself a string, the unprintable character "\036". It allows one to distinguish between native bash strings and Lisp pointers. Any string of which the first character is $tag_marker is considered a pointer to a non-string type.
• nnn is a 3-character string of an integer with leading zeros that represents the "type tag". gherkin currently supports 3 non-string types, each of which has a corresponding tag.
• ddd... is the "data" portion of the pointer, and can be arbitrarily long. Integer objects store their printed representation here. conses store their pointer here, an integer into the car and cdr arrays. symbols store a pointer here into the symbols array.

For instance, the + primitive function accepts two arguments, each of which is understood to be a pointer to a Lisp object. It expects each object to be an integer - as of this writing no type checking is done. $tag_marker and type tag are stripped from each pointer, and the remaining substrings - strings representing integers - are added together via bash's $((x + y)).

Note: gherkin strings are native. Another way, gherkin string pointers represent themselves and are discerned by not having $tag_marker at the front.