# Decision tables

Decision tables is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
 This page uses content from Wikipedia. The original article was at Decision Table. The list of authors can be seen in the page history. As with Rosetta Code, the text of Wikipedia is available under the GNU FDL. (See links for details on variance)

Decision Tables are a precise yet compact way to model complicated logic.

Demonstrate how your language implements decision tables.

Use this example of Printer Troubleshooting given in the Wikipedia article.

First the specification of a generic decision table package:

`generic   type Condition is (<>);   type Action is (<>);   with function Ask_Question (Cond: Condition) return Boolean;   with procedure Give_Answer (Act:  Action);   with procedure No_Answer; package Generic_Decision_Table is    type Answers is array(Condition) of Boolean;   type Rule_R is record      If_Then: Answers;      Act:     Action;   end record;   type Rule_A is array(Positive range <>) of Rule_R;    procedure React(Rules: Rule_A); end Generic_Decision_Table; `

Next, the implementation of the generic decision table package:

`package body Generic_Decision_Table is   procedure React(Rules: Rule_A) is      A: Answers;      Some_Answer: Boolean := False;   begin      for C in A'Range loop         A(C) := Ask_Question(C);      end loop;      for R in Rules'Range loop         if A = Rules(R).If_Then then            Give_Answer(Rules(R).Act);            Some_Answer := True;         end if;      end loop;      if not Some_Answer then         No_Answer;      end if;   end React; end Generic_Decision_Table; `

That was easy! Now we implement the printer troubleshooting application:

`with Generic_Decision_Table, Ada.Text_IO; procedure Printer_Decision_Table is    type Condition is (Does_Not_Print, Red_Light_Flashing, Unrecognised);   type Action is (Power_Cable, Printer_Computer_Cable, Software_Installed,                   New_Ink, Paper_Jam);    function Question(Cond: Condition) return Boolean is      use Ada.Text_IO;      Ch: Character;   begin      case Cond is         when Does_Not_Print =>            Put("Printer does not print?");         when Red_Light_Flashing =>            Put("A red light is flashing?");         when Unrecognised =>            Put("Printer is unrecognised?");      end case;      Put_Line (" y/Y => 'yes', any other input: 'no'");      Get(Ch);      return (Ch='y') or (Ch='Y');   end Question;    procedure Answer(Act: Action) is      use Ada.Text_IO;   begin      case Act is         when Power_Cable =>            Put_Line("Check the power cable!");         when Printer_Computer_Cable =>            Put_Line("Check the printer-computer cable!");         when Software_Installed =>            Put_Line("Ensure the printer software is installed!");         when New_Ink =>            Put_Line("Check/replace ink!");         when Paper_Jam =>            Put_Line("Check for paper jam!");      end case;   end Answer;    procedure No_Answer is   begin      Ada.Text_IO.Put_Line("Sorry! I have no idea what to do now!");   end No_Answer;    package DT is new Generic_Decision_Table     (Condition, Action, Question, Answer, No_Answer);    R: DT.Rule_A := (((True,  False, True),  Power_Cable),                    ((True,  True,  True),  Printer_Computer_Cable),                    ((True,  False, True),  Printer_Computer_Cable),                    ((True,  True,  True),  Software_Installed),                    ((True,  False, True),  Software_Installed),                    ((False, True,  True),  Software_Installed),                    ((False, False, True),  Software_Installed),                    ((True,  True,  True),  New_Ink),                    ((True,  True,  False), New_Ink),                    ((False, True,  True),  New_Ink),                    ((False, True,  False), New_Ink),                    ((True,  True,  False), Paper_Jam),                    ((True,  False, False), Paper_Jam)                   ); begin   DT.React(R);end Printer_Decision_Table;`

Sample output:

```> ./printer_decision_table
Printer does not print? y/Y => 'yes', any other input: 'no'
y
A red light is flashing? y/Y => 'yes', any other input: 'no'
n
Printer is unrecognised? y/Y => 'yes', any other input: 'no'
n
Check for paper jam!

> ./printer_decision_table
Printer does not print? y/Y => 'yes', any other input: 'no'
y
A red light is flashing? y/Y => 'yes', any other input: 'no'
y
Printer is unrecognised? y/Y => 'yes', any other input: 'no'
n
Check/replace ink!
Check for paper jam!

> ./printer_decision_table
Printer does not print? y/Y => 'yes', any other input: 'no'
n
A red light is flashing? y/Y => 'yes', any other input: 'no'
n
Printer is unrecognised? y/Y => 'yes', any other input: 'no'
n
Sorry! I have no idea what to do now!```

## AutoHotkey

`Conditions =(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 unrecognized			|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| | | | |) Condition:=[], Action:=[], Correlation:=[]loop, parse, Conditions, `n{    No:= A_Index, 	RegExMatch(A_LoopField, "^(.*?)\t+(.*)", m),	Cond%No% := m1    for k, v in StrSplit(m2, "|")	Condition[No, k] := v="Y"?1:0}loop, parse, Actions, `n{    No:= A_Index	, RegExMatch(A_LoopField, "^(.*?)\t+(.*)", m),	Act%No% := m1    for k, v in StrSplit(m2, "|")	Action[No, A_Index] := v="X"?1:0} loop, % Condition.MaxIndex(){    j := A_Index,	    CondLine:=ActLine:=""    loop, % Condition.MaxIndex()	CondLine .= Condition[A_Index,j]    loop, % Action.MaxIndex()	ActLine.= Action[A_Index,j]?1:0    Correlation[CondLine]:=ActLine} Gui, font,, CourierGui, add, text, w456Gui, add, text, wp h1 0x7 y+0loop, parse, Conditions, `n{    Gui, add, text, y+0 , % A_LoopField    Gui, add, text, wp h1 0x7 y+0}Gui, add, text, wp Gui, add, text, wp h1 0x7 y+0loop, parse, Actions, `n{    Gui, add, text, y+0 , % A_LoopField    Gui, add, text, wp h1 0x7 y+0}Gui, add, text, wp loop, % Condition.MaxIndex()    Gui, add, Checkbox,vC%A_Index% gSubmit wp h15, % Cond%A_Index%Gui, add, text, wp , take the following actions(s):AM := Action.MaxIndex()Gui, add, Edit, vOutput ReadOnly r%AM% wp -TabStopGui, showreturn Submit:Gui, Submit, NoHideCondLine:=Res:=""loop, % Condition.MaxIndex()    CondLine.= C%A_Index%MyCorr := Correlation[CondLine]loop, parse, MyCorr    if A_LoopField	Res .= Act%A_Index% "`n"GuiControl,, Output, % Resreturn`

## AWK

` # syntax: GAWK -f DECISION_TABLES.AWK DECISION_TABLES.TXTBEGIN {    FS = ":"}{   if (\$0 ~ /^#/) { # comment      next    }    if (rule_length == 0) { # 1st rule      rule_length = length(\$2)    }    if (rule_length != length(\$2)) {      error(sprintf("FILENAME=%s, FNR=%d, rule length not consistent with previous lengths, %s",FILENAME,FNR,\$0))    }    if (\$1 == "C") { # condition      if (\$2 !~ /^[NY]+\$/) {        error(sprintf("FILENAME=%s, FNR=%d, rule S/B 'N' or 'Y', %s",FILENAME,FNR,\$0))      }      c_arr[++c] = \$2 SUBSEP \$3    }    else if (\$1 == "A") { # action      if (\$2 !~ /^[X-]+\$/) {        error(sprintf("FILENAME=%s, FNR=%d, rule S/B 'X' or '-', %s",FILENAME,FNR,\$0))      }      a_arr[++a] = \$2 SUBSEP \$3    }}END {    validate_rules()    if (errors > 0) { exit(1) }    show_actions(ask_conditions())    exit(0)}function ask_conditions(  ans,i,key) {    print("condtions:")    for (i=1; i<=c; i++) {      while (1) {        printf("  %s? ",getext(c_arr[i]))        getline ans <"con"        if (ans ~ /^[nNyY]/) {          key = key toupper(substr(ans,1,1))          break        }      }    }    return(key)}function getext(str) {    return(substr(str,index(str,SUBSEP)+1))}function show_actions(user_reply,  hits,i,key) {    key = key_arr[user_reply]    print("actions:")    for (i=1; i<=a; i++) {      if (substr(a_arr[i],key,1) == "X") {        printf("  %s\n",getext(a_arr[i]))        hits++      }    }    printf("%d found\n",hits)}function validate_rules(  i,j,key) {    for (i=1; i<=rule_length; i++) {      key = ""      for (j=1; j<=c; j++) {        key = key substr(c_arr[j],i,1)      }      if (key in key_arr) {        error(sprintf("duplicate key: %s",key))      }      key_arr[key] = i    }}function error(message) {    printf("error: %s\n",message)    errors++    return} `

decision table:

```# RULES    CONDITIONS
C:YYYYNNNN:Printer does not print
C:YYNNYYNN:A red light is flashing
C:YNYNYNYN:Printer is unrecognized
# RULES    ACTIONS
A:--X-----:Check the power cable
A:X-X-----:Check the printer-computer cable
A:X-X-X-X-:Ensure printer software is installed
A:XX--XX--:Check/replace ink
A:-X-X----:Check for paper jam
```

Output:

```condtions:
Printer does not print? Y
A red light is flashing? Y
Printer is unrecognized? Y
actions:
Check the printer-computer cable
Ensure printer software is installed
Check/replace ink
3 found

condtions:
Printer does not print? N
A red light is flashing? N
Printer is unrecognized? N
actions:
0 found
```

## C

With flaky keyboard input:
`#include <stdio.h> #define N_COND 3#define COND_LEN (1 << N_COND) struct { const char *str, *truth;}cond[N_COND] = {	{"Printer does not print",		"1111...."},	{"A red light is flashing",		"11..11.."},	{"Printer is unrecognised",		"1.1.1.1."},},solu[] = {	{"Check the power cable",		"..1....."},	{"Check the printer-computer cable",	"1.1....."},	{"Ensure printer software is installed","1.1.1.1."},	{"Check/replace ink",			"11..11.."},	{"Check for paper jam",			".1.1...."},}; int main(){	int q, ans, c; 	for (q = ans = c = 0; q < N_COND; q++) {		do {			if (c != '\n') printf("%s? ", cond[q].str);			c = getchar();		} while (c != 'y' && c != 'n');		ans = (ans << 1) | (c != 'y');	} 	if (ans == COND_LEN - 1)		printf("\nSo, you don't have a problem then?\n");	else {		printf("\nSolutions:\n");		for (q = 0; q < sizeof(solu)/sizeof(solu); q++)			if (solu[q].truth[ans] == '1')				printf("    %s\n", solu[q].str);	}	return 0;}`
output
`Printer does not print? yA red light is flashing? nPrinter is unrecognised? y Solutions:    Check the power cable    Check the printer-computer cable    Ensure printer software is installed`

## COBOL

`        >> SOURCE FORMAT FREEidentification division.program-id. 'decisiontable'. environment division.configuration section.repository.    function all intrinsic. data division. working-storage section. 01  conditions.    03  notprinting pic x.    03  flashing pic x.    03  notrecognized pic x. procedure division.start-decision-table. display space  display 'The printer does not print (Y or N) ' with no advancingaccept notprinting display 'A red light is flashing (Y or N) ' with no advancingaccept flashing display 'The printer is unrecognized (Y or N) ' with no advancingaccept notrecognized move upper-case(conditions) to conditions display space *>decision table Printer troubleshooter *>  conditions*>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 unrecognized              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 *>end decision table evaluate notprinting also flashing also notrecognized when 'Y' also 'Y' also 'Y'    display 'Check the printer-computer cable'    display 'Ensure printer software is installed'    display 'Check/replace ink' when 'Y' also 'Y' also 'N'    display 'Check/replace ink'    display 'Check for paper jam' when 'Y' also 'N' also 'Y'    display 'Check the power cable'    display 'Check the printer-computer cable'    display 'Ensure printer software is installed' when 'Y' also 'N' also 'N'    display 'Check for paper jam' when 'N' also 'Y' also 'Y'    display 'Ensure printer software is installed'    display 'Check/replace ink' when 'N' also 'Y' also 'N'    display 'Check/replace ink' when 'N' also 'N' also 'Y'    display 'Ensure printer software is installed' when 'N' also 'N' also 'N'    display 'no action found' when other    display 'invalid input: ' notprinting space flashing space notrecognized end-evaluate display space stop run. end program 'decisiontable'. `
Output:
```\$ cobc -xj decisiontable.cob

The printer does not print (Y or N) n
A red light is flashing (Y or N) n
The printer is unrecognized (Y or N) y

Ensure printer software is installed
```

## D

`import std.stdio, std.algorithm, std.exception, std.array; immutable struct DecisionTable {    alias immutable(bool)[] IBA;    const string[] conds,  actions;    immutable IBA[IBA] rules;     private static immutable(bool[]) growTo(in bool[] b,                                            in size_t newLen)    pure nothrow {        auto result = new bool[newLen];        result[0 .. b.length] = b[];        return result.assumeUnique;    }     this(immutable string[] c,         immutable string[] a,         immutable bool[][][] q) pure nothrow {        conds = c;        actions = a;        IBA[IBA] r;        foreach (p; q)            r[growTo(p, conds.length)] =                growTo(p, actions.length);        rules = r.assumeUnique;    }     string[] test(in bool[] tested,                  in string NoMatchMsg="It is fine :)")    const pure nothrow {        string[] rightActions;        auto iTested = growTo(tested, conds.length);        if (iTested in rules)            foreach (immutable i, immutable e; rules[iTested])                if (e)                    rightActions ~= actions[i];         if (!rightActions.empty)            return rightActions;        return [NoMatchMsg];    }     void consult() const {        bool[] query;         foreach (cond; conds) {            write(cond, "? [y=yes/others=no] ");            string answer = "no";            try                answer = stdin.readln;            catch (StdioException)                writeln("no");            query ~= !!answer.startsWith('y', 'Y');        }         writefln("%-(%2s\n%)", test(query));    }} void main() {    enum { F = false, T = true }    immutable d = immutable(DecisionTable)(            ["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"],              [[[T, F, F], [F, F, T]],              [[F, T, F], [F, F, F, T]],              [[T, T, F], [F, F, T, T]],              [[F, F, T], [F, F, F, F, T]],              [[T, F, T], [T, T, T]],              [[F, T, T], [F, F, F, T, T]],              [[T, T, T], [F, T, T, T, F]]             ]        );     d.consult;}`
Output:
```Printer is unrecognised? [y=yes/others=no] no
A red light is flashing? [y=yes/others=no] no
Printer does not print? [y=yes/others=no] no
It is fine :)```

### Alternative Version

Translation of: C
`import std.stdio, std.string; struct DataPair(size_t N) {    string message;    immutable char[N] truth;} immutable DataPair!8[] conditions = [    {"Printer does not print",               "####...."},    {"A red light is flashing",              "##..##.."},    {"Printer is unrecognised",              "#.#.#.#."}]; immutable DataPair!8[] solutions = [    {"Check the power cable",                "..#....."},    {"Check the printer-computer cable",     "#.#....."},    {"Ensure printer software is installed", "#.#.#.#."},    {"Check/replace ink",                    "##..##.."},    {"Check for paper jam",                  ".#.#...."}]; void main() {    size_t code = 0;     foreach (immutable cond; conditions) {        write(cond.message, "? [y=yes/others=no] ");        string answer = "no";        try            answer = stdin.readln();        catch (StdioException)            writeln("no");        code = (code << 1) | !answer.startsWith('y', 'Y');    }     if (code == (2 ^^ conditions.length) - 1)        writeln("\nSo, you don't have a problem then?");    else {        writeln("\nSolutions:");        foreach (immutable sol; solutions)            if (sol.truth[code] == '#')                writeln("    ", sol.message);    }}`
Output:
```Printer does not print? [y=yes/others=no] no
A red light is flashing? [y=yes/others=no] no
Printer is unrecognised? [y=yes/others=no] no

So, you don't have a problem then?```

## Go

Go has no specific support for decision tables, but they can be implemented easily. With a little ingenuity, literal data can be arranged in rows and columns in a way that preserves the visual associations of decision tables. Go has an init function that might be useful for compiling decision tables at program startup. And Go maps allow efficient lookup of actions given conditions.

`package main import (    "errors"    "fmt"    "os") type dtText struct {    rules, text string} var ptText = []dtText{    {"YYYYNNNN", "Printer does not print"},    {"YYNNYYNN", "A red light is flashing"},    {"YNYNYNYN", "Printer is unrecognised"},    {"--------", ""},    {"  X     ", "Check the power cable"},    {"X X     ", "Check the printer-computer cable"},    {"X X X X ", "Ensure printer software is installed"},    {"XX  XX  ", "Check/replace ink"},    {" X X    ", "Check for paper jam"},} type dtMap map[string][]string func compileDT(t []dtText) (dtMap, error) {    if len(t) == 0 {        return nil, errors.New("Empty decision table")    }    var conditions, actions []dtText    ruleColumns := len(t.rules)    for i, row := range t {        if len(row.rules) != ruleColumns {            return nil, errors.New("Inconsistent number of rule columns")        }        if len(row.text) == 0 {            if conditions != nil {                return nil, errors.New("Multple separator lines")            }            if i == 0 {                return nil, errors.New("No conditions specified")            }            if i == len(t)-1 {                return nil, errors.New("No actions specified")            }            conditions = t[:i]            actions = t[i+1:]        }    }    if conditions == nil {        return nil, errors.New("Missing separator line")    }    m := make(map[string][]string, ruleColumns)    kb := make([]byte, len(conditions))    for col := 0; col < ruleColumns; col++ {        for i, c := range conditions {            kb[i] = c.rules[col]        }        key := string(kb)        for _, a := range actions {            if a.rules[col] != ' ' {                m[key] = append(m[key], a.text)            }        }    }    return m, nil} func init() {    var err error    if ptMap, err = compileDT(ptText); err != nil {        fmt.Println(err)        os.Exit(1)    }} var ptMap dtMap func main() {    for _, a := range ptMap["NYY"] {        fmt.Println(a)    }}`

Output:

```Ensure printer software is installed
Check/replace ink
```

## Icon and Unicon

`record cond(text,flags)record  act(text,flags,aflags) procedure main()   DT := [      cond("Printer does not print",                  "YYYYNNNN"),      cond("A red light is flashing",		      "YYNNYYNN"),      cond("Printer is unrecognised",		      "YNYNYNYN"),      ,                                            # separator       act("Check the power cable",		      "NNYNNNNN"),      act("Check the printer-computer cable",	      "YNYNNNNN"),      act("Ensure printer software is installed",     "YNYNYNYN"),      act("Check/replace ink",			      "YYNNYYNN"),      act("Check for paper jam",		      "NYNYNNNN") ]    every (act := [])[1 to *DT] := ''               # empty csets for actions   ans := ''                                       # empty answer cset   every d := DT[i := 1 to *DT] do {      /conds := list(*d.flags,'')      case type(d) of {         "cond":{            sel := cset(&cset[i])                  # selector for this cond            ans ++:= ( ask(d.text) == "Y", sel)    # ... add to answer            every j := 1 to *conds do              # assemble condition flags               if d.flags[j] == "Y" then conds[j] ++:= sel            }         "act":{            d.aflags := list(*conds,'')            every j := 1 to *conds do {               if d.flags[j] == "Y" then                   d.aflags[j] := conds[j]          # matching conditions               if d.aflags[j] == ans                   then write(d.text)               # matched, write action               }            }         default: write("----------------------------")   # separator          }      }end procedure ask(text)repeat {   writes(text," ? ")   a := map(trim(read()),&lcase,&ucase)   case a of {       "Y": return a      "N": fail      default: write(a," is an invalid response, enter a Y or N, ")       }   }end`
Sample Output:
```Printer does not print ? Y
A red light is flashing ? N
Printer is unrecognised ? N
----------------------------
Check for paper jam```

## J

Solution:
`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' =/&;: RULESRULE_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'={[email protected]@[email protected](1!:1)@1:@[email protected],&'?'@dtb"1 q   (,~ ('/'cut'Suggested resolutions:/Solution unknown.') {::~ 0=#) options)`
Example (solution found):
`   troubleshoot ''Having trouble?  Let's track down the problem: 	Printer does not print?Y 	A red light is flashing?Y 	Printer is unrecognised?YSuggested resolutions:                 	Check the printer-computer cable     	Ensure printer software is installed 	Check/replace ink                   `
`   troubleshoot ''Having trouble?  Let's track down the problem:	Printer does not print?N	A red light is flashing?N	Printer is unrecognised?NSolution unknown. `

The only interesting line in this solution is the one that assigns RULE_TABLE. 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) 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.

## JavaScript

### Interactive

Since this is an interactive web page, results can't be listed. See http://jsfiddle.net/rGP6C/1/ for a live demo.

`<html><head></head><body>    <form id="form"></form>    <br/>Possible solutions:    <ul id="ul"></ul></body><script src="http://code.jquery.com/jquery-latest.min.js"></script><script type="text/javascript">    var questions = [        { bools:[1,1,1,1,0,0,0,0], text:"Printer does not print" },        { bools:[1,1,0,0,1,1,0,0], text:"A red light is flashing" },        { bools:[1,0,1,0,1,0,1,0], text:"Printer is unrecognized" },    ];    var answers = [        { bools:[0,0,1,0,0,0,0,0], text:"Check the power cable" },        { bools:[1,0,1,0,0,0,0,0], text:"Check the printer-computer cable" },        { bools:[1,0,1,0,1,0,1,0], text:"Ensure printer software is installed" },        { bools:[1,1,0,0,1,1,0,0], text:"Check/replace ink" },        { bools:[0,1,0,1,0,0,0,0], text:"Check for paper jam" },    ]     \$(document).ready(function() {        // Init form with questions. "Value" is a descending power of 2.        var value = questions.bools.length;        for (var i = 0; i < questions.length; i++) {            value /= 2;            var el = '<br /><input type="checkbox" value="' + value + '">' + questions[i].text;            \$("#form").append(el);        }         // Respond to a checkbox action.        \$('input:checkbox').change(function() {             // Figure out which combination of checkboxes the user selected.            var sum = 0;            \$('input:checkbox:checked').each(function () {                sum += Number(this.value);            });             // Translate sum into an index (column #) into bools.            var index = questions.bools.length - sum - 1;             // Clear the answers.            \$('#ul').html('');             // Add appropriate answers.            for (var i = 0; i < answers.length; i++) {                if (answers[i].bools[index]) {                    \$('#ul').append('<li>' + answers[i].text + '</li>')                }            }        });    });</script></html>`

### DecTab object

This implements a DecisionTable object called `DecTab`. The JavaScript dialect is Microsoft's JScript.

` var DecTab = function () {  this.conditions = [];  this.rules = [];  this.actions = [];} DecTab.prototype.Conditions = function () {  var args = [].slice.call(arguments);  for (var i = 0; i < args.length; i++) {    this.conditions.push(args[i]);  }  return this;}; DecTab.prototype.RulesActions = function (rules, actions) {  var count = 0;  var actionable;  this.rules.push(rules)  this.actions.push(actions);  return this;}; DecTab.prototype.Decide = function () {  var decision = [];  var decided = false;  for (var i = 0; i < this.conditions.length; i++) {    decision.push((this.conditions[i]()));  }  var decisionstring = "." + decision.join(".") + ".";   for (i = 0; i < this.rules.length; i++) {    var rule = [];    for (var j = 0; j < this.rules[i].length; j++) {      rule.push((this.rules[i][j]));    }    var rulestring = "." + rule.join(".") + ".";    if (rulestring === decisionstring) {      decided = true;      for (var k = 0; k < this.actions[i].length; k++) {        this.actions[i][k]();      }      break;    }  }  if (!decided) {    WScript.Echo("No decision table rows matched.");  }} `

The task is rendered as follows

`   function Ask(q) {    WScript.StdOut.Write(q);    WScript.StdOut.Write(" [Y/N]?");    var ans = WScript.StdIn.ReadLine();    ans = ans.substr(0, 1).toUpperCase() === "Y" ? "Y" : "N";    return ans;  }  function Tell(w) {    WScript.Echo(w);  }   function Check_the_power_cable() {    Tell("Check the power cable.");  }  function Check_the_printer_computer_cable() {    Tell("Check the printer-computer cable.");  }  function Ensure_printer_software_is_installed() {    Tell("Ensure printer software is installed.");  }  function Check_replace_ink() {    Tell("Check/replace ink.");  }  function Check_for_paper_jam() {    Tell("Check for paper jam.");  }   function Printer_Prints() {    return Ask("Printer prints");  }  function A_red_light_is_flashing() {    return Ask("A red light is flashing");  }  function Printer_is_recognized_by_computer() {    return Ask("Printer is recognized by computer");  }   var DT = new DecTab()  .Conditions(    Printer_Prints,    A_red_light_is_flashing,    Printer_is_recognized_by_computer)  .RulesActions(["N", "Y", "N"], [Check_the_printer_computer_cable, Ensure_printer_software_is_installed, Check_replace_ink])  .RulesActions(["N", "Y", "Y"], [Check_replace_ink, Check_for_paper_jam])  .RulesActions(["N", "N", "N"], [Check_the_power_cable, Check_the_printer_computer_cable, Ensure_printer_software_is_installed])  .RulesActions(["N", "N", "Y"], [Check_for_paper_jam])  .RulesActions(["Y", "Y", "N"], [Ensure_printer_software_is_installed, Check_replace_ink])  .RulesActions(["Y", "Y", "Y"], [Check_replace_ink])  .RulesActions(["Y", "N", "N"], [Ensure_printer_software_is_installed])  .RulesActions(["Y", "N", "Y"], [])  .Decide(); `

And a sample run

` C:\>CScript DecisionTable.jsPrinter prints [Y/N]?YA red light is flashing [Y/N]?YPrinter is recognized by computer [Y/N]?YCheck/replace ink. `

## Julia

Translation of: Perl
`const queries = [("Printer does not print",  0b11110000),                  ("A red light is flashing", 0b11001100),                 ("Printer is unrecognised", 0b10101010)] const answers = Dict(0b00100000 => "Check the power cable",                     0b10100000 => "Check the printer-computer cable",                     0b10101010 => "Ensure printer software is installed",                     0b11001100 => "Check/replace ink",                     0b01010000 => "Check for paper jam",                     0b00000001 => "Cannot diagnose any problem.") function ynprompt(prompt)    while true        print(prompt, "?: ")        if (ans = strip(uppercase(readline()))) in ['Y', 'N']            return ans        end    endend function decide(queries, answers)    cond = 0b11111111    for (prompt, value) in queries        cond &= (ynprompt(prompt) == 'Y' ? value : UInt8(~value))    end    for (bitpat, diagnosis) in answers        if cond & bitpat != 0            println(diagnosis)        end    endend decide(queries, answers) `
Output:
```Printer does not print?: y
A red light is flashing?: y
Printer is unrecognised?: n
Check/replace ink
Check for paper jam
```

## Kotlin

`// version 1.1.51 val conditions = listOf(    "Printer prints"                    to "NNNNYYYY",    "A red light is flashing"           to "YYNNYYNN",    "Printer is recognized by computer" to "NYNYNYNY") val actions = listOf(    "Check the power cable"                to "NNYNNNNN",    "Check the printer-computer cable"     to "YNYNNNNN",    "Ensure printer software is installed" to "YNYNYNYN",     "Check/replace ink"                    to "YYNNNYNN",    "Check for paper jam"                  to "NYNYNNNN") fun main(args: Array<String>) {    val nc = conditions.size    val na = actions.size    val nr = conditions.second.length  // number of rules    val np = 7  // index of 'no problem' rule    println("Please answer the following questions with a y or n:")    val answers = BooleanArray(nc)    for (c in 0 until nc) {        var input: String        do {            print("  \${conditions[c].first} ? ")            input = readLine()!!.toUpperCase()        }        while (input != "Y" && input != "N")        answers[c] = (input == "Y")    }    println("\nRecommended action(s):")    outer@ for (r in 0 until nr) {        for (c in 0 until nc) {            val yn = if (answers[c]) 'Y' else 'N'            if (conditions[c].second[r] != yn) continue@outer        }        if (r == np) {            println("  None (no problem detected)")        }        else {            for (a in 0 until na) {                if (actions[a].second[r] == 'Y') println("  \${actions[a].first}")            }        }        return    }}`

Sample input/output:

```Please answer the following questions with a y or n:
Printer prints ? n
A red light is flashing ? n
Printer is recognized by computer ? n

Recommended action(s):
Check the power cable
Check the printer-computer cable
Ensure printer software is installed
```

## Perl

`use strict;use warnings; sub decide {    our(@q,%a);    local *q = shift;    local *a = shift;    my \$bit;    my \$cnt = 1;    for my \$prompt (@q) {        print "\$prompt: ";        \$bit += \$cnt if <> =~ /y/i;        \$cnt *= 2;    }    \$bit = 2**\$bit;     while (my (\$bitpat,\$diagnosis) = each %a) {        print "\$diagnosis\n" if \$bit & \$bitpat;    }} my @queries = (    'Printer is unrecognised',    'A red light is flashing',    'Printer does not print',);my %answers = (    0b00100000 => 'Check the power cable',    0b10100000 => 'Check the printer-computer cable',    0b10101010 => 'Ensure printer software is installed',    0b11001100 => 'Check/replace ink',    0b01010000 => 'Check for paper jam',); decide(\@queries,\%answers);`
Output:
```Printer is unrecognised: n
A red light is flashing: n
Printer does not print: y
Check for paper jam```

## Perl 6

`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 '';}`

A bit of explanation: we pass in two pair lists for the questions and solutions; we ignore the keys of the questions, since they can be generated by regarding them as a binary counter from right to left, with the least significant bit on the bottom. The @q.map 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.) We sum up those powers of two using a [+] reduction metaoperator, which in this case gives us a number from 0 to 7. Then we take 2 to that power.

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 || on lists as well as scalars to provide a default result if nothing matches.

Output:
```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```

## Phix

Written such that conditions and actions could easily be read from a plain text file, and should cope fairly well with different lengths, missing/conflicting options, etc.

`constant conditions = """YYYYNNNN:Printer does not printYYNNYYNN:A red light is flashingYNYNYNYN:Printer is unrecognized"""constant actions = """--X-----:Check the power cableX-X-----:Check the printer-computer cableX-X-X-X-:Ensure printer software is installedXX--XX--:Check/replace ink-X-X----:Check for paper jam""" procedure validate(sequence s, integer l, string letters, name)    if remainder(length(s),2) then        throw(sprintf("uneven %s pairings",{name}))    end if    for i=1 to length(s) by 2 do        string si = s[i]        if length(si)!=l then            throw(sprintf("mismatched lengths (line %d)",i))        end if        for j=1 to length(si) do            if not find(si[j],letters) then                throw(sprintf("invalid letter [%c not in %s]",{si[j],letters}))            end if        end for    end forend procedure constant qa = split_any(conditions,"\n:",no_empty:=true),         sa = split_any(actions,"\n:",no_empty:=true)integer l = length(qa) function ask_questions()    sequence valid = repeat(true,l)    integer a    for i=1 to length(qa) by 2 do        while true do            puts(1,qa[i+1]&":? ")            a = upper(wait_key())            if find(a,"YN") then exit end if                    puts(1,"\nplease enter Y or N\n")        end while        printf(1,"%c\n",a)        for j=1 to l do            if a!=qa[i][j] then valid[j] = false end if        end for    end for    return validend function procedure show_answers(integer k)    integer count = 0    for i=1 to length(sa) by 2 do        if sa[i][k]='X' then            puts(1,sa[i+1]&"\n")            count += 1        end if    end for    printf(1,"%d answers\n",count)end procedure procedure main()    try        validate(qa,l,"YN","condition")        validate(sa,l,"-X","action")    catch e        ?e        abort(0)    end try    sequence valid = ask_questions()    integer sv = sum(valid)    if sv=0 then        puts(1,"no answers")    elsif sv=1 then        show_answers(find(true,valid))    else        puts(1,"multiple answer sets\n")        for i=1 to length(valid) do            if valid[i] then                printf(1,"for %d:\n",i)                show_answers(i)            end if        end for    end ifend proceduremain()`
Output:
```Printer does not print:? N
A red light is flashing:? Y
Printer is unrecognized:? Y
Ensure printer software is installed
Check/replace ink
```

## PicoLisp

We allow ourselves a luxurious user interface:

`(de yes? (Cond)   (out NIL (prin (car Cond) "? "))   (in NIL      (use Reply         (loop            (setq Reply (read))            (T (member Reply '(T Y YES Yes y yes true 1))               T )            (T (member Reply '(NIL N NO No n no false 0)))            (prinl "Please answer 'Yes' or 'No'") ) ) ) )`

The decision table used in the example:

`(de *Conditions   ("Printer does not print"                T   T   T   T  NIL NIL NIL NIL)   ("A red light is flashing"               T   T  NIL NIL  T   T  NIL NIL)   ("Printer is unrecognised"               T  NIL  T  NIL  T  NIL  T  NIL) ) (de *Actions   ("Check the power cable"                NIL NIL  T)   ("Check the printer-computer cable"      T  NIL  T)   ("Ensure printer software is installed"  T  NIL  T  NIL  T  NIL  T)   ("Check/replace ink"                     T   T  NIL NIL  T   T)   ("Check for paper jam"                  NIL  T  NIL  T) )`

The decision can be made directly on the condition and action data, without the need to create intermediate tables:

`(de decide ()   (let Reply (mapcar yes? *Conditions)      (extract and         (apply pick (append *Conditions *Actions)            '(@               (unless (pick '((Flg) (<> Flg (next))) Reply)                  (rest) ) ) )         (mapcar car *Actions) ) ) )`

Output:

```: (decide)
Printer does not print? y
A red light is flashing? y
Printer is unrecognised? n
-> ("Check/replace ink" "Check for paper jam")

: (decide)
Printer does not print? n
A red light is flashing? y
Printer is unrecognised? y
-> ("Ensure printer software is installed" "Check/replace ink")

: (decide)
Printer does not print? n
A red light is flashing? n
Printer is unrecognised? n
-> NIL```

## 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 for x in action2rules]    # Map condition to actions    rule2actions = dict((y,[]) for y in set(sum((x 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)`

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!```

## Racket

This implementation shows off the 2d language. The "Actions" could be a square array of empty and X boxes. I thought it might be fun to merge them.

`#lang unstable/2d racket (define (ask-y/n q)  (printf "~a [y/n]?" q)  (define (get-y/n)    (match (read-line)      [(? eof-object?) eof]      [(regexp #rx"^[yY]") #t]      [(regexp #rx"^[nN]") #f]      [_ (printf "reply yes or no, please:") (get-y/n)]))  (get-y/n)) (define (cells->hash grid)  (for*/hash ((block (in-list grid)) (address (in-list (car block))))    (values address (match (cdr block)                      ['(N) #f]                      ['(Y) #t]                      ['(X) 'X]                      [else else])))) (define (run-decision-table tbl)  (match-define (list '2ddecision_table col-widths row-heights all-cells ...) tbl)   ;; after this, the rules without an X are removed  (define full-cells (filter (match-lambda [(list _ _ _ ...) #t] [_ #f]) all-cells))   ;; cell addresses are (list column row)  (match-define    (list-no-order     `((,_ ... (1 1) ,_ ...)                           ,caption ...)     `(((,rules-columns ,_) ...)                        Rules)     `(((,(app add1 text-columns) ,condition-rows) ...) Conditions)     `(((,_ ,action-rows) ...)                          Actions)     remaining-cells ...)    full-cells)   (define remaining-cells# (cells->hash remaining-cells))  (define (cell# c r (dflt #f))    (hash-ref remaining-cells# (list c r) dflt))   (define text-column (first text-columns))   (let question-loop ((remain-conds condition-rows) (remain-acts action-rows))    (match remain-conds      [(list) (displayln "I give up... read the manual or something.")]      [(list conds-h conds-t ...)       (match (ask-y/n (string-join (map ~a (cell# text-column conds-h)) " "))         [(? eof-object?) "bye!"]         [y/n-response          (define remain-acts-            (for/list                ((action remain-acts)                 #:when (for/first                            ((rule-c (in-list rules-columns))                             #:when (eq? (cell# rule-c conds-h) y/n-response) ; matches rule flag                             #:when (equal? (cell# rule-c action #f) 'X)) ; has an X                          #t))              action))          (match remain-acts-            [(list) (printf "No more actions... no more suggestions from the rules!~%")]            [(list only-action) (printf "Suggested action: ~s~%" (cell# text-column only-action))]            [_ (question-loop conds-t remain-acts-)])])]))) (define printer-troubleshooting-2dtable  '#2ddecision_table  ╔═╦════════════╦════════════════════════════════════════════╦═╦═╦═╦═╦═╦═╦═╦═╗  ║ ║            ║                                            ║ ║ ║ ║ ║ ║ ║ ║ ║  ╠═╬════════════╩════════════════════════════════════════════╬═╩═╩═╩═╩═╩═╩═╩═╣  ║ ║ Printer troubleshooter                                  ║ Rules         ║  ╠═╬════════════╦════════════════════════════════════════════╬═══════╦═══════╣  ║ ║ Conditions ║ Printer does not print                     ║Y      ║N      ║  ╠═╣            ╠════════════════════════════════════════════╣   ╔═══╬═══╗   ║  ║ ║            ║ A red light is flashing                    ║   ║N  ║Y  ║   ║  ╠═╣            ╠════════════════════════════════════════════╣ ╔═╬═╗ ║ ╔═╬═╗ ║  ║ ║            ║ Printer is unrecognized                    ║ ║N║Y║ ║ ║N║Y║ ║  ╠═╬════════════╬════════════════════════════════════════════╬═╩═╬═╬═╩═╩═╩═╩═╣  ║ ║ Actions    ║ Check the power cable                      ║   ║X║         ║  ╠═╣            ╠════════════════════════════════════════════╬═╗ ║ ║         ║  ║ ║            ║ Check the printer-computer cable           ║X║ ║ ║         ║  ╠═╣            ╠════════════════════════════════════════════╣ ║ ║ ║ ╔═╗ ╔═╗ ║  ║ ║            ║ Ensure printer software is installed       ║ ║ ║ ║ ║X║ ║X║ ║  ╠═╣            ╠════════════════════════════════════════════╣ ╚═╬═╝ ║ ╚═╬═╝ ║  ║ ║            ║ Check/replace ink                          ║   ║   ║   ║   ║  ╠═╣            ╠════════════════════════════════════════════╬═╗ ║ ╔═╬═══╝   ║  ║ ║            ║ Check for paper jam                        ║ ║ ║ ║X║       ║  ╚═╩════════════╩════════════════════════════════════════════╩═╩═╩═╩═╩═══════╝) (run-decision-table printer-troubleshooting-2dtable)`
Output:

A trial run...

```Printer does not print [y/n]?n
A red light is flashing [y/n]?y
Printer is unrecognized [y/n]?n
Suggested action: (Check/replace ink)```

## REXX

This REXX example shows how one version of a decision table could be implemented,

•   a   no solution found   message
•   a   don't care   requirement   (regarding the decision table)
•   a method of specifying requirements and not needing recoding for future queries
•   used a minimalistic way in expressing the decision table
•   extra prompting when there was a user response error
•   handles superfluous blanks and some punctuation.
•   displaying of a countdown so user knows length of interrogation
•   visual fidelity aids for postmortem analysis (as in logs)
•   a method of allowing the user to quit (opt-out of) the interrogation
`/*REXX program demonstrates a (query)  decision table  and  possible corrective actions.*/Q.=;      Q.1 = 'Does the printer not print?'          Q.2 = 'Is there a red light flashing on the printer?'          Q.3 = 'Is the printer unrecognized by the software?'          Q.0 =  3action.=            /* Y=yes       N=no        if character isn't a letter = don't care.*/       /*    ┌─────◄── answer to 1st question     (it can be in upper\lower\mixed case). */      /*    │┌────◄──   "     " 2nd    "           "  "   "  "   "     "     "     "    */      /*    ││┌───◄──   "     " 3rd    "           "  "   "  "   "     "     "     "    */      /*    │││                                                                         */      /*    ↓↓↓                                                                         */action.1 = 'yny'  ;         pos.1 = 'Check the power cable.'action.2 = 'y.y'  ;         pos.2 = 'check the printer-computer cable.'action.3 = '..y'  ;         pos.3 = 'Ensure printer software is installed.'action.4 = '.y.'  ;         pos.4 = 'Check/replace ink.'action.5 = 'y.n'  ;         pos.5 = 'Check for paper jam.'       do i=1  for Q.0;   ans.i=asker(i);   end   /*display the question, obtain response*/say                                              /*display a blank line before questions*/possible=0                                       /*we'll be counting possible solutions.*/   do k=1  while action.k\==''                    /*filter the answers via decision table*/                 do j=1;      d=substr(action.k, j, 1);           upper d                jm=j//Q.0;   if jm==0  then jm=Q.0                if d==' '              then leave                if \datatype(d, 'U')   then iterate                if d\==ans.jm          then iterate k                if j==Q                then leave                end   /*j*/  say pos.k                                      /*this could be a possible solution.   */  possible=possible+1                            /*count number of possible solutions.  */  end       /*k*/ if possible==0  then say 'No solutions given for the information supplied.'exit                                             /*stick a fork in it,  we're all done. *//*──────────────────────────────────────────────────────────────────────────────────────*/asker:  arg ?;   oops=0;         Qprefix=copies('─', 9)   '(question'   ?   "of"   Q.0') 'howTo = '(You can answer with a  Yes or No   [or  Quit])'   do forever  if oops  then do;  say;  say right(howTo,79);   say;   oops=0;   end  say Qprefix Q.?;         parse pull x                    /*ask question (after prompt)*/  x=strip(space(x),,'.');  parse upper var x  u  1  u1  2  /*u1=1st character of answer.*/  if words(x)==0         then iterate                      /*Nothing entered? Try again.*/  if abbrev('QUIT',u,1)  then exit                         /*user is tired of answering.*/  if (abbrev('YES',u) | abbrev("NO",u)) & words(x)==1  then return u1  say 'invalid response: '   x;          oops=1  end   /*forever*/`

output   (a screen scraping using a DOS prompt window for the possible responses) DECISION.REX is the REXX program that produced this output.

```D:\►rexx decision

───────── (question 1 of 3)  Does the printer not print?
no
───────── (question 2 of 3)  Is there a red light flashing on the printer?
No
───────── (question 3 of 3)  Is the printer unrecognized by the software?
n

No solutions given for the information supplied.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
n
───────── (question 2 of 3)  Is there a red light flashing on the printer?
n
───────── (question 3 of 3)  Is the printer unrecognized by the software?
yes

Ensure printer software is installed.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
n
───────── (question 2 of 3)  Is there a red light flashing on the printer?
Ye
───────── (question 3 of 3)  Is the printer unrecognized by the software?
n

Check/replace ink.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
n
───────── (question 2 of 3)  Is there a red light flashing on the printer?
yes.
───────── (question 3 of 3)  Is the printer unrecognized by the software?
yes

Ensure printer software is installed.
Check/replace ink.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
y
───────── (question 2 of 3)  Is there a red light flashing on the printer?
no
───────── (question 3 of 3)  Is the printer unrecognized by the software?
no

Check for paper jam.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
y
───────── (question 2 of 3)  Is there a red light flashing on the printer?
n
───────── (question 3 of 3)  Is the printer unrecognized by the software?
y

Check the power cable.
check the printer-computer cable.
Ensure printer software is installed.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
y
───────── (question 2 of 3)  Is there a red light flashing on the printer?
y
───────── (question 3 of 3)  Is the printer unrecognized by the software?
n

Check/replace ink.
Check for paper jam.

D:\►rexx decision
───────── (question 1 of 3)  Does the printer not print?
y
───────── (question 2 of 3)  Is there a red light flashing on the printer?
y
───────── (question 3 of 3)  Is the printer unrecognized by the software?
y

check the printer-computer cable.
Ensure printer software is installed.
Check/replace ink.

D:\►
```

## Ring

` # Project : Decision tables see "The printer does not print (Y or N) "give notprintingsee "A red light is upper(flashing) (Y or N) "give flashingsee "The printer is unrecognized (Y or N) "give notrecognized if upper(notprinting) = "Y" and upper(flashing) = "Y" and upper(notrecognized) = "Y"   see "Check the printer-computer cable" + nl   see "Ensure printer software is installed" + nl   see "Check/replace ink"elseif upper(notprinting) = "Y" and upper(flashing) = "Y" upper(notrecognized) = "N"        see "Check/replace ink" + nl        see "Check for paper jam" + nlelseif upper(notprinting) = "Y" and  upper(flashing) = "N" and upper(notrecognized) = "Y"        see "Check the power cable"        see "Check the printer-computer cable" + nl        see "Ensure printer software is installed" + nlelseif upper(notprinting) = "Y" and upper(flashing) = "N" and upper(notrecognized) = "N"        see "Check for paper jam" + nlelseif upper(notprinting) = "N" and upper(flashing) = "Y" and upper(notrecognized) = "Y"        see "Ensure printer software is installed" + nl        see "Check/replace ink" + nlelseif upper(notprinting) = "N" and upper(flashing) = "Y" and upper(notrecognized) = "N"        see "Check/replace ink" + nlelseif upper(notprinting) = "N" and upper(flashing) = "N" and upper(notrecognized) = "Y"        see "Ensure printer software is installed" + nlelseif upper(notprinting) = "N" and upper(flashing) = "N" and upper(notrecognized) = "N"        see "no action found" + nlelse        see "invalid input: " + upper(notprinting) + " " + upper(flashing) + " " + upper(notrecognized) + nlok `

Output:

```The printer does not print (Y or N) y
A red light is upper(flashing) (Y or N) y
The printer is unrecognized (Y or N) y
Check the printer-computer cable
Ensure printer software is installed
Check/replace ink
```

## 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  endend 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}`

Example

```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:

## Sidef

Translation of: Perl 6
`func decide (q, s) {     var bits = q.map { |p|        read("#{p.value}? ", String) ~~ /^y/i ? 1 : 0    }     var n = with (0) { |t|        bits.each { |b|            t <<= 1            t |= b        }        1 << t    }     s.grep { .key & n }.map{ .value }.each { |ans|        say "   #{ans}"    }} loop {    decide(      [        Pair("Y Y Y Y N N N N", "Printer does not print"),        Pair("Y Y N N Y Y N N", "A red light is flashing"),        Pair("Y N Y N Y N Y N", "Printer is unrecognised"),      ],      [        Pair(0b0_0_1_0_0_0_0_0, "Check the power cable"),        Pair(0b1_0_1_0_0_0_0_0, "Check the printer-computer cable"),        Pair(0b1_0_1_0_1_0_1_0, "Ensure printer software is installed"),        Pair(0b1_1_0_0_1_1_0_0, "Check/replace ink"),        Pair(0b0_1_0_1_0_0_0_0, "Check for paper jam"),      ]    )    say ''}`
Output:
```Printer does not print? y
A red light is flashing? n
Printer is unrecognised? n
Check for paper jam

Printer does not print? n
A red light is flashing? n
Printer is unrecognised? y
Ensure printer software is installed

Printer does not print? y
A red light is flashing? y
Printer is unrecognised? n
Check/replace ink
Check for paper jam

Printer does not print? n
A red light is flashing? y
Printer is unrecognised? y
Ensure printer software is installed
Check/replace ink

Printer does not print? ^C
```

## Tcl

`package require TclOO #http://rosettacode.org/wiki/Keyboard_Input/Obtain_a_Y_or_N_response#Tclproc yesno {{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	    }	}    }}`

Demonstration:

`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`

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
```