# Unu: Simple, Literate Source Files

RETRO is written in a literate style. Most of the sources
are in a format called Unu. This allows easy mixing of
commentary and code blocks, making it simple to document
the code.

The Unu format does not support writing code and commentary "out
of order".

As an example,

    # Determine The Average Word Name Length

    To determine the average length of a word name two values
    are needed. First, the total length of all names in the
    Dictionary:

    ~~~
    #0 [ d:name s:length + ] d:for-each
    ~~~

    And then the number of words in the Dictionary:

    ~~~
    #0 [ drop n:inc ] d:for-each
    ~~~

    With these, a simple division is all that's left.

    ~~~
    /
    ~~~

    Finally, display the results:


    ~~~
    'Average_name_length:_%n\n s:format s:put
    ~~~

This illustrates the format. Only code in the fenced blocks
(between \~~~ pairs) get extracted and run.

(Note: this only applies to *source files*; fences are not used
when entering code interactively).

## On The Name

The name Unu comes from the Maori language, where it means:

    (verb) (-hia) pull out, withdraw, draw out, extract.
    Taken from https://maoridictionary.co.nz/