# Forth Kata

## Instructions

Implement an evaluator for a very simple subset of Forth.

[Forth](https://en.wikipedia.org/wiki/Forth_%28programming_language%29) is a stack-based
programming language. Implement a very basic evaluator for a small subset of Forth.

Your evaluator has to support the following words:

 * `+`, `-`, `*`, `/` (integer arithmetic)
 * `DUP`, `DROP`, `SWAP`, `OVER` (stack manipulation)

Your evaluator also has to support defining new words using the customary syntax:

```forth
: word-name definition ;
```

To keep things simple the only data type you need to support is signed integers of at least 16 bits size.

You should use the following rules for the syntax: a number is a sequence of one or more (ASCII) digits,
a word is a sequence of one or more letters, digits, symbols or punctuation that is not a number.
(Forth probably uses slightly different rules, but this is close enough.)

Words are case-insensitive.