Levels

The Cat specification is divided into several different levels of compatibility. Different Cat implementations may have varying degrees of compatibility with the Cat standard. For example a Cat implementation that provides the complete set of Level-0 primitives, and only some of the Level-1 primitives would be said to be a "Level-0 Compliant Implementation of Cat".

Each level of compliance implies that all lower levels are also fully supplied.

Level-0, Level-1 and Level-2 do not permit side-effects. Level-3 and above do.

A Level-0 Cat implementation provides only a small set of functions for operating on the following types: int, bool, var, and list. For a list of all Level-0 primitives see http://www.cat-language.com/primitives.html#level0

A Level-1 Cat implementation provides a large set of predefined primitive functions that can all be built entirely from Level-0 primitives. For a list of all Level-1 primitives see http://www.cat-language.com/primitives.html#level1

A Level-2 Cat implementation introduces additional types: byte, char, string, dbl, bit, byte_block, hash_list.

A Level-3 Cat implementation introduces dynamic function dispatching based on type (ad-hoc polymorphism) and exceptions.

A Level-4 Cat implementation introduces features that require an operating system. Level-4 compliance requires the following types: istream, ostream.

A Level-5 Cat implementation introduces features that require a graphical user interface. Level-5 Cat allows side-effects.

For More Information

http://www.cat-language.com/manual.html#compat