LAC is a laconic lisp interpreter.

Lexically scoped, single-namespace, extensible.

This is mostly a free time hack to learn lisp internals.

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Extensibility: How to add new types

1. Create a C file containing:

- Three type specific functions
  - 'eq
  - 'print
  - 'eval

- an INIT function that register the ext_type to the system (will be
  automatically executed at runtime, no need to change the main file)

2. Add lexer rules to scan and allocate the new type in 'atoms.l

3. Debug