[EXIM] Opinion sought: filter variables

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Author: Philip Hazel
Date:  
To: exim-users
Subject: [EXIM] Opinion sought: filter variables
It has been suggested that writing filter files would be made easier if
some kind of "scoring" facility were available. It has also been
suggested that user variables be implemented. I feel that a full-blown
implementation of variables would amount to a mini programming language
and would be getting out of hand. On the other hand, a very simple
scoring system with a command like "score <n>" provides in effect just
one variable, which is a bit restricting (though less so than no
variables :-).

What do people think about the following compromise:

10 numeric variables are available with the names n0 - n9. They start
out with a value of zero when a filter file is entered. Their values
can be changed by the command

add <number> to <name>

where negative numbers are permitted. Their values can be used in
other commands by variable expansions such as $n0.

A simple scoring scheme could be implemented by something like

if <condition 1> then add 1 to n1 endif
if <condition 2> then add 2 to n1 endif
if <condition 3> then add -1 to n1 endif
if <condition 4> then add 1 to n1 endif
if $n1 above 3 then seen finish endif
if $n1 above 0 then freeze endif

with more complicated schemes making use of more than one variable.

Opinions, please!

-- 
Philip Hazel                   University Computing Service,
ph10@???             New Museums Site, Cambridge CB2 3QG,
P.Hazel@???          England.  Phone: +44 1223 334714



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