Decision tables: Difference between revisions
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=={{header|J}}== |
=={{header|J}}== |
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'''Solution''':<lang j>require'strings' |
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( , (,.~'_NAMES',L:0~]) ;:'RULES ACTIONS' ) =: , > split&.|:L:1 }.&.> (split~ (<'Actions:') i.&1@:= {."1) }."1 TAB cut&> LF cut noun define |
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Printer troubleshooter: |
Printer troubleshooter: |
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Printer does not print Y Y Y Y N N N N |
Printer does not print Y Y Y Y N N N N |
Revision as of 02:34, 31 January 2011
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.
J
Solution:<lang j>require'strings' ( , (,.~'_NAMES',L:0~]) ;:'RULES ACTIONS' ) =: , > split&.|:L:1 }.&.> (split~ (<'Actions:') i.&1@:= {."1) }."1 TAB cut&> LF cut noun define
Printer troubleshooter: 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 Actions: 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
)
boxIdx =: <"1@:(<"0) RULE_TABLE =: ACTIONS ( (<,'X') = [ )`([: boxIdx (<,'Y') = ])`(0 $~ (,~ $&2)&({:@$)) } RULES
troubleshoot =: verb define
RULE_TABLE troubleshoot~ RULES_NAMES ,&< ACTIONS_NAMES
'R A'=.x smoutput 'Having trouble? Lets track down the problem:' > (,~ (<;._2'Suggested resolutions: /Solution unknown./') {~ 0=#) TAB,&.> A #~ y {~ boxIdx (<,'Y')=toupper@:(1!:1)@:1:@:smoutput@:(TAB , ,&'?')&.> R
)</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 RULE_TABLE. The rest is mostly ancillary support. This is because the task highlights some freedoms J's multidimensional nature provides to the programmer.
Here, we create an array with as many axes (dimensions) as there are rules (questions), plus one. All axes, except the last, have 2 points (to wit: false, true). The last axis contains a boolean vector indicating which actions to try (or not). Thus, J's multidimensional array is leveraged as a tree, and the user's answers provide a path to a leaf (which is accessed arraywise, i.e. all at once).
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) troubleshoot 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.
D
<lang d>import std.stdio, std.algorithm, std.exception, std.string, std.array, std.conv ;
struct Decision {
alias immutable(byte)[] IBA ; immutable string[] conds ; immutable string[] actions ; immutable IBA[IBA] rules ;
this(string[] c, string[] a, byte[][][] q) { conds = c.idup ; actions = a.idup ; IBA[IBA] r ; foreach(p ; q) { p[0].length = conds.length ; p[1].length = actions.length ; r[p[0].idup] = p[1].idup ; } rules = assumeUnique(r) ; }
string[] test(bool[] tested, string NoMatchMsg = "it is fine :)") { byte[] testedBytes = array(map!"to!byte(a?1:0)"(tested)) ; return test(testedBytes, NoMatchMsg) ; } string[] test(byte[] tested, string NoMatchMsg = "it is fine :)") { string[] rightActions ; tested.length = conds.length ; auto rule = tested.idup in rules ; if(rule !is null) foreach(i, e ; *rule) if(e) rightActions ~= actions[i] ; if(rightActions.length > 0) return rightActions ; return [NoMatchMsg] ; }
void consult() { bool[] query ; string answer ; foreach(c;conds) { write(c,"? [y=yes/others=no] ") ; readf("%s\n", &answer) ; query ~= (answer.length > 0 && answer.tolower[0..1] == "y") ; } writeln(test(query).join("\n")) ; }
}
void main() {
Decision d = Decision( ["Printer is unrecognised", "A red light is flashing", "Printer does not print"], ["Check the power cable", "Check the printer-computer cable", "Ensure printer software is installed", "Check/replace ink", "Check for paper jam"], [[[1,0,0],[0,0,1]], [[0,1,0],[0,0,0,1]], [[1,1,0],[0,0,1,1]], [[0,0,1],[0,0,0,0,1]], [[1,0,1],[1,1,1]], [[0,1,1],[0,0,0,1,1]], [[1,1,1],[0,1,1,1,0]] ] ) ; d.consult() ;
}</lang> Sample output:
Printer is unrecognised? [y=yes/others=no] y A red light is flashing? [y=yes/others=no] y Printer does not print? [y=yes/others=no] n Ensure printer software is installed Check/replace ink
Python
<lang python> Create a Decision table then use it
def dt_creator():
print("\n\nCREATING THE DECISION TABLE\n") conditions = input("Input conditions, in order, separated by commas: ") conditions = [c.strip() for c in conditions.split(',')] print( ("\nThat was %s conditions:\n " % len(conditions)) + '\n '.join("%i: %s" % x for x in enumerate(conditions, 1)) ) print("\nInput an action, a semicolon, then a list of tuples of rules that trigger it. End with a blank line") action2rules, action = [], ' ' while action: action = input("%i: " % (len(action2rules) + 1)).strip() if action: name, _, rules = [x.strip() for x in action.partition(';')] rules = eval(rules) assert all(len(rule) == len(conditions) for rule in rules), \ "The number of conditions in a rule to trigger this action is wrong" action2rules.append((name, rules)) actions = [x[0] for x in action2rules] # Map condition to actions rule2actions = dict((y,[]) for y in set(sum((x[1] for x in action2rules), []))) for action, rules in action2rules: for r in rules: rule2actions[r].append( action ) return conditions, rule2actions
def dt_user(dt, default=['Pray!']):
conditions, rule2actions = dt print("\n\nUSING THE DECISION TABLE\n") rule = tuple(int('y' == input("%s? (Answer y if statement is true or n): " % c)) for c in conditions) print("Try this:\n " + '\n '.join(rule2actions.get(rule, default)))
if __name__ == '__main__':
dt = dt_creator() dt_user(dt) dt_user(dt) dt_user(dt)</lang>
Sample Run
CREATING THE DECISION TABLE Input conditions, in order, separated by commas: Printer does not print, A red light is flashing, Printer is unrecognised That was 3 conditions: 1: Printer does not print 2: A red light is flashing 3: Printer is unrecognised Input an action, a semicolon, then a list of tuples of rules that trigger it. End with a blank line 1: Check the power cable; [(1,0,1)] 2: Check the printer-computer cable; [(1,1,1), (1,0,1)] 3: Ensure printer software is installed; [(1,1,1), (1,0,1), (0,1,1), (0,0,1)] 4: Check/replace ink; [(1,1,1), (1,1,0), (0,1,1), (0,1,0)] 5: Check for paper jam; [(1,1,0), (1,0,0)] 6: USING THE DECISION TABLE Printer does not print? (Answer y if statement is true or n): n A red light is flashing? (Answer y if statement is true or n): y Printer is unrecognised? (Answer y if statement is true or n): y Try this: Ensure printer software is installed Check/replace ink USING THE DECISION TABLE Printer does not print? (Answer y if statement is true or n): y A red light is flashing? (Answer y if statement is true or n): n Printer is unrecognised? (Answer y if statement is true or n): y Try this: Check the power cable Check the printer-computer cable Ensure printer software is installed USING THE DECISION TABLE Printer does not print? (Answer y if statement is true or n): n A red light is flashing? (Answer y if statement is true or n): n Printer is unrecognised? (Answer y if statement is true or n): n Try this: Pray!
Tcl
<lang tcl>package require TclOO
proc yesno Template:Message "Press Y or N to continue" {
fconfigure stdin -blocking 0 exec stty raw read stdin ; # flush puts -nonewline "${message}: " flush stdout while {![eof stdin]} { set c [string tolower [read stdin 1]] if {$c eq "y" || $c eq "n"} break } puts [string toupper $c] exec stty -raw fconfigure stdin -blocking 1 return [expr {$c eq "y"}]
}
oo::class create DecisionTable {
variable qlist responses constructor {questions responseMap} {
set qlist $questions set responses $responseMap
}
method consult {} {
set idx 0 foreach q $qlist { set answer [yesno "$q? \[y/n\]"] set idx [expr {$idx*2 + (1-$answer)}] } foreach {msg map} $responses { # Allow a column to be omitted; magic! if {"0[lindex $map $idx]"} { puts $msg } }
}
}</lang> Demonstration: <lang tcl>DecisionTable create printerDiagnosisTable {
"Printer does not print" "A red light is flashing" "Printer is unrecognised"
} {
"Check the power cable" {0 0 1} "Check the printer-computer cable" {1 0 1} "Ensure printer software is installed" {1 0 1 0 1 0 1} "Check/replace ink" {1 1 0 0 1 1} "Check for paper jam" {0 1 0 1}
} printerDiagnosisTable consult</lang> Output:
Printer does not print? [y/n]: N A red light is flashing? [y/n]: Y Printer is unrecognised? [y/n]: Y Ensure printer software is installed Check/replace ink