Decision tables: Difference between revisions

=={{header|Ruby}}==

<lang ruby>class DecisionTable

def initialize(conditions, actions)

@conditions = conditions

@actions = []

@rules = []

actions.each {|action, ruleset| @actions << action; @rules << ruleset}

end

def run

puts "Conditions:"

index = ask_conditions

puts "Actions:"

results = @rules.each_with_index.inject([]) do |sum, (ruleset, idx)|

sum << @actions[idx] if ruleset[index] == 1

sum

end

results << "PC LOAD LETTER" if results.empty?

results.each {|res| puts " #{res}"}

puts ""

end

private

def ask_conditions

answers = @conditions.inject("") {|sum, c| sum + get_response(c)}

answers.to_i(2)

end

def get_response(prompt)

loop do

print " #{prompt}? "

case STDIN.gets.strip.downcase

when /^y/ then return "0"

when /^n/ then return "1"

end

end

end

end

dt = DecisionTable.new(

[

"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

],

[

["Check the power cable", [0,0,1,0,0,0,0,0]],

["Check the printer-computer cable", [1,0,1,0,0,0,0,0]],

["Ensure printer software is installed", [1,0,1,0,1,0,1,0]],

["Check/replace ink", [1,1,0,0,1,1,0,0]],

["Check for paper jam", [0,1,0,1,0,0,0,0]],

]

)

loop {dt.run}</lang>

Example

<pre>Conditions:

Printer does not print? y

A red light is flashing? y

Printer is unrecognised? y

Actions:

Check the printer-computer cable

Ensure printer software is installed

Check/replace ink

Conditions:

Printer does not print? y

A red light is flashing? y

Printer is unrecognised? n

Actions:

Check/replace ink

Check for paper jam

Conditions:

Printer does not print? y

A red light is flashing? n

Printer is unrecognised? y

Actions:

Check the power cable

Check the printer-computer cable

Ensure printer software is installed

Conditions:

Printer does not print? y

A red light is flashing? n

Printer is unrecognised? n

Actions:

Check for paper jam

Conditions:

Printer does not print? n

A red light is flashing? y

Printer is unrecognised? y

Actions:

Ensure printer software is installed

Check/replace ink

Conditions:

Printer does not print? n

A red light is flashing? y

Printer is unrecognised? n

Actions:

Check/replace ink

Conditions:

Printer does not print? n

A red light is flashing? n

Printer is unrecognised? y

Actions:

Ensure printer software is installed

Conditions:

Printer does not print? n

A red light is flashing? n

Printer is unrecognised? n

Actions:

PC LOAD LETTER</pre>