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Decision tables: Difference between revisions
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For large numbers of rules and few actions, J's native support of sparse arrays might provide a performance advantage, particularly in space. A minor note about the implementation here: the verb (function) <tt>troubleshoot</tt> is generalized, and reusable on any set of rule table, questions, and suggested actions. The default is to use those given in the printer troubleshooting table.
=={{header|Perl 6}}==
<lang perl6>sub decide (@q, @s) {
my $bit = 2 ** [+] (1,2,4...*) Z* reverse @q.map: {
so prompt(.value ~ "? ") ~~ /:i ^y/;
}
say " $_" for @s.grep(*.key +& $bit)».value || "No clue!";
}
loop {
decide
(
"Y Y Y Y N N N N" => "Printer does not print",
"Y Y N N Y Y N N" => "A red light is flashing",
"Y N Y N Y N Y N" => "Printer is unrecognised",
),
(
:2<0_0_1_0_0_0_0_0> => "Check the power cable",
:2<1_0_1_0_0_0_0_0> => "Check the printer-computer cable",
:2<1_0_1_0_1_0_1_0> => "Ensure printer software is installed",
:2<1_1_0_0_1_1_0_0> => "Check/replace ink",
:2<0_1_0_1_0_0_0_0> => "Check for paper jam",
);
say '';
}</lang>
A bit of explanation: we pass in two pair lists for the question and solutions; the <tt>@q.map</tt> runs the prompts and maps them to booleans
using case-insensitive matching. We reverse that list and zip multiply with powers of two to figure out which bit we're going to grep for. (The zip stops on the shorter list, which is always going to be the list of booleans, since the list of powers of two is infinite.) The solutions list of pairs is conveniently keyed on binary numbers written in colon radix notation, so we grep the keys containing the correct bit, then map the pair list to its values using a hyperoperator to parallelize it. Unlike in Perl 5, we can use <tt>||</tt> on lists as well as scalars to provide a default result if nothing matches.
{{out}}
<pre>Printer does not print? n
A red light is flashing? y
Printer is unrecognised? n
Check/replace ink
Printer does not print? y
A red light is flashing? n
Printer is unrecognised? y
Check the power cable
Check the printer-computer cable
Ensure printer software is installed
Printer does not print? n
A red light is flashing? n
Printer is unrecognised? n
No clue!
Printer does not print? ^C</pre>
=={{header|PicoLisp}}==
We allow ourselves a luxurious user interface:
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