retroforth/doc/book/Programming-Techniques-Unu

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# 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.
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).