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Heron-Centric: Ruminations of a Language Designer
Cat version 0.9.9
by Christopher Diggins
January 26, 2007
The Cat programming language is fast approaching 1.0 status!


I have recently posted a new version of the Cat interpreter ( so that people at large can start poking and prodding it with a stick before I release it as 1.0.

For those unfamiliar with Cat, it is a functional stack-based programming language with a type system. It looks like if ML and Forth had a baby. it is a very concise and powerful language. It is a pure functional language, but still allows side-effects in a very controlled manner (without all of the confusing Monad stuff that Haskell has).

The Cat interpreter is entirely public domain (that means you can do virtually whatever you want with it without obligations or restrictions). The source code is written in C# and is tested on Mono (but only on my Windows implementation of it). I'd be curious how it works out for people on other systems.

The type system underwent a recent redesign, but the language works great even without a type checker. I plan on reintroducing the type-checking and type-inference engine in version 2.0. However the semantics of the type system have been ratified, and are explained at least semi-formally at

Please share your thoughts, suggestions, questions and criticisms!

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About the Blogger

Christopher Diggins is a software developer and freelance writer. Christopher loves programming, but is eternally frustrated by the shortcomings of modern programming languages. As would any reasonable person in his shoes, he decided to quit his day job to write his own ( ). Christopher is the co-author of the C++ Cookbook from O'Reilly. Christopher can be reached through his home page at

This weblog entry is Copyright © 2007 Christopher Diggins. All rights reserved.

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