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Decision tables: Difference between revisions
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{{draft task}}
[[wp:Decision_table|Decision Tables]] are a precise yet compact way to model complicated logic. Demonstrate how your language implements decision tables. Use the example of Printer Troubleshooting given in the Wikipedia article.
=={{header|D}}==
Line 135 ⟶ 79:
Ensure printer software is installed
Check/replace ink</pre>
=={{header|J}}==
'''Solution''':<lang j>require'strings'
'RULE_NAMES RULES'=: |:':'&cut;._2 noun define
Printer does not print: Y Y Y Y N N N N
A red light is flashing: Y Y N N Y Y N N
Printer is unrecognised: Y N Y N Y N Y N
)
'ACTION_NAMES ACTIONS'=: |:':'&cut;._2 noun define
Check the power cable: - - X - - - - -
Check the printer-computer cable: X - X - - - - -
Ensure printer software is installed: X - X - X - X -
Check/replace ink: X X - - X X - -
Check for paper jam: - X - X - - - -
)
assert (-:~.)|: 'Y' =/&;: RULES
RULE_TABLE=: (,/'X'=/&;: ACTIONS) /:&|: 'Y' =/&;: RULES
troubleshoot =: verb define
RULE_TABLE troubleshoot~ RULE_NAMES ,&< ACTION_NAMES
:
'q a'=.x
smoutput 'Having trouble? Let''s track down the problem:'
options=. a #~ y {~ #. 'Y'={.@toupper@deb@(1!:1)@1:@smoutput@,&'?'@dtb"1 q
(,~ ('/'cut'Suggested resolutions:/Solution unknown.') {::~ 0=#) options
)</lang>
'''Example''' (''solution found''):<lang j> troubleshoot ''
Having trouble? Let's track down the problem:
Printer does not print?
Y
A red light is flashing?
Y
Printer is unrecognised?
Y
Suggested resolutions:
Check the printer-computer cable
Ensure printer software is installed
Check/replace ink </lang>
'''Example''' (''solution not found''):<lang j> troubleshoot ''
Having trouble? Let's track down the problem:
Printer does not print?
N
A red light is flashing?
N
Printer is unrecognised?
N
Solution unknown.
</lang>
=== Comments ===
The only interesting line in this solution is the one that assigns <tt>RULE_TABLE</tt>. The rest is mostly ancillary support.
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|PicoLisp}}==
We allow ourselves a luxurious user interface:
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