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From: Lew Pitcher <lew.pitcher@digitalfreehold.ca>
Newsgroups: comp.lang.c
Subject: Re: ASCII to ASCII compression.
Date: Mon, 10 Jun 2024 00:45:08 -0000 (UTC)
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On Thu, 06 Jun 2024 17:25:37 +0100, Malcolm McLean wrote:

> Not strictly a C programming question, but smart people will see the 
> relavance to the topicality, which is portability.
> 
> Is there a compresiion algorthim which converts human language ASCII 
> text to compressed ASCII, preferably only "isgraph" characters?
> 
> So "Mary had a little lamb, its fleece was white as snow".
> 
> Would become
> 
> QWE£$543GtT£$"||x|VVBB?

I'm afraid that you have conflicting requirements here. In effect,
you want to take an array of values (each within the range of
0 to 127) and
a) make the array shorter ("compress it"), and
b) express the individual elements of this shorter array with
   a range of 96 values ("isgraph() characters")

Because you reduce the number of values each result element
can carry, each result element can only express a fraction
(96/128'ths) of the corresponding source element. Thus,
with the isgraph() requirement, the result will take /more/
elements to express the same data as the source did.

However, you want /compression/, which implies that you want
the result to be smaller than the source. And, therein lies
the conflict.

Can you help clarify this for me?
-- 
Lew Pitcher
"In Skills We Trust"