# Decision tables

(Redirected from 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.

## 11l

Translation of: Kotlin
V conditions = [
(‘Printer prints’                   , ‘NNNNYYYY’),
(‘A red light is flashing’          , ‘YYNNYYNN’),
(‘Printer is recognized by computer’, ‘NYNYNYNY’)]

V actions = [
(‘Check the power cable’               , ‘NNYNNNNN’),
(‘Check the printer-computer cable’    , ‘YNYNNNNN’),
(‘Ensure printer software is installed’, ‘YNYNYNYN’),
(‘Check/replace ink’                   , ‘YYNNNYNN’),
(‘Check for paper jam’                 , ‘NYNYNNNN’)]

V nr = conditions[0][1].len
V np = 7

L(condition) conditions
V inp = ‘’
L
inp = input(‘  ’condition[0]‘ ? ’).uppercase()
I inp C (‘Y’, ‘N’)
L.break

print("\nRecommended action(s):")
L(r) 0 .< nr
L(c) 0 .< conditions.len
V yn = I answers[c] {‘Y’} E ‘N’
I conditions[c][1][r] != yn
L.break
L.was_no_break
I r == np
print(‘  None (no problem detected)’)
E
L(action) actions
I action[1][r] == ‘Y’
print(‘  ’action[0])
L.break
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


First the specification of a generic decision table package:

generic
type Condition is (<>);
type Action is (<>);
with function Ask_Question (Cond: Condition) return Boolean;

package Generic_Decision_Table is

type Answers is array(Condition) of Boolean;
type Rule_R is record
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
begin
for C in A'Range loop
end loop;
for R in Rules'Range loop
if A = Rules(R).If_Then then
end if;
end loop;
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
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;

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;

begin
Ada.Text_IO.Put_Line("Sorry! I have no idea what to do now!");

package DT is new Generic_Decision_Table

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[1].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,, Courier
Gui, add, text, wp h1 0x7 y+0
loop, parse, Conditions, n
{
Gui, add, text, y+0 , % A_LoopField
Gui, add, text, wp h1 0x7 y+0
}
Gui, add, text, wp h1 0x7 y+0
loop, parse, Actions, n
{
Gui, add, text, y+0 , % A_LoopField
Gui, add, text, wp h1 0x7 y+0
}
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, show
return

Submit:
Gui, Submit, NoHide
CondLine:=Res:=""
loop, % Condition.MaxIndex()
CondLine.= C%A_Index%
MyCorr := Correlation[CondLine]
loop, parse, MyCorr
if A_LoopField
Res .= Act%A_Index% "n"
GuiControl,, Output, % Res
return


## AWK

# syntax: GAWK -f DECISION_TABLES.AWK DECISION_TABLES.TXT
BEGIN {
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) }
exit(0)
}
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))
}
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[0]); q++)
if (solu[q].truth[ans] == '1')
printf("    %s\n", solu[q].str);
}
return 0;
}


output

Printer does not print? y
A red light is flashing? n
Printer is unrecognised? y

Solutions:
Check the power cable
Check the printer-computer cable
Ensure printer software is installed


## C++

Translation of: Java
#include <iostream>
#include <string>
#include <vector>

const std::vector<std::pair<std::string, std::string>> conditions = {
{"Printer prints", "NNNNYYYY"},
{"A red light is flashing", "YYNNYYNN"},
{"Printer is recognized by computer", "NYNYNYNY"}
};

const std::vector<std::pair<std::string, std::string>> actions = {
{"Check the power cable", "NNYNNNNN"},
{"Check the printer-computer cable", "YNYNNNNN"},
{"Ensure printer software is installed", "YNYNYNYN"},
{"Check/replace ink", "YYNNNYNN"},
{"Check for paper jam", "NYNYNNNN"},
};

int main() {
const size_t nc = conditions.size();
const size_t na = actions.size();
const size_t nr = conditions[0].second.size();
const int np = 7;

std::string input;

std::cout << "Please answer the following questions with a y or n:\n";
for (size_t c = 0; c < nc; c++) {
char ans;
do {
std::cout << conditions[c].first << "? ";

std::getline(std::cin, input);
ans = std::toupper(input[0]);
} while (ans != 'Y' && ans != 'N');
}

std::cout << "Recommended action(s)\n";
for (size_t r = 0; r < nr; r++) {
for (size_t c = 0; c < nc; c++) {
char yn = answers[c] ? 'Y' : 'N';
if (conditions[c].second[r] != yn) {
goto outer;
}
}
if (r == np) {
std::cout << "  None (no problem detected)\n";
} else {
for (auto action : actions) {
if (action.second[r] == 'Y') {
std::cout << "  " << action.first << '\n';
}
}
}
break;

outer: {}
}

return 0;
}

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

## COBOL

        >> SOURCE FORMAT FREE
identification 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 advancing
accept notprinting

display 'A red light is flashing (Y or N) ' with no advancing
accept flashing

display 'The printer is unrecognized (Y or N) ' with no advancing
accept 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[0], conds.length)] = growTo(p[1], 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? Keyboard handling is sketchy, just type "true" or "false" to each question. ## FreeBASIC dim as boolean rules(0 to 2, 0 to 7) =_ { {false, false, false, false, true, true, true, true},_ { true, true, false, false, true, true, false, false},_ {false, true, false, true, false, true, false, true} } dim as boolean actions(0 to 4, 0 to 7) =_ { {false, false, true, false, false, false, false, false},_ { true, false, true, false, false, false, false, false},_ { true, false, true, false, true, false, true, false},_ { true, true, false, false, false, true, false, false},_ {false, true, false, true, false, false, false, false} } dim as string rule_names(0 to 2) =_ {"Printer prints", "A red light is flashing",_ "Printer is recognized by computer"} dim as string action_names(0 to 4) = _ {"Check the power cable", "Check the printer-computer cable",_ "Ensure printer software is installed", "Check/replace ink",_ "Check for paper jam" } dim as boolean answers(0 to 2) for i as uinteger = 0 to 2 print rule_names(i), input answers(i) next i print "---- Suggested solutions: ----" for i as uinteger = 0 to 4 for j as uinteger = 0 to 7 if not actions(i, j) then continue for for k as uinteger = 0 to 2 if rules(k, j)<>answers(j) then goto dontdoit next k print action_names(i) dontdoit: next j next i ## 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[0].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' =/&;: 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 )  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? Y Suggested resolutions: Check the printer-computer cable Ensure printer software is installed Check/replace ink  Example (solution not found):  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.  ### Comments 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. ## Java Translation of: Kotlin import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.List; import java.util.Objects; public class DecisionTables { private static class Pair<T, U> { private final T t; private final U u; public static <T, U> Pair<T, U> of(T t, U u) { return new Pair<>(t, u); } public Pair(T t, U u) { this.t = t; this.u = u; } public T getFirst() { return t; } public U getSecond() { return u; } } private static final List<Pair<String, String>> conditions = List.of( Pair.of("Printer prints", "NNNNYYYY"), Pair.of("A red light is flashing", "YYNNYYNN"), Pair.of("Printer is recognized by computer", "NYNYNYNY") ); private static final List<Pair<String, String>> actions = List.of( Pair.of("Check the power cable", "NNYNNNNN"), Pair.of("Check the printer-computer cable", "YNYNNNNN"), Pair.of("Ensure printer software is installed", "YNYNYNYN"), Pair.of("Check/replace ink", "YYNNNYNN"), Pair.of("Check for paper jam", "NYNYNNNN") ); public static void main(String[] args) throws IOException { final int nc = conditions.size(); final int na = actions.size(); final int nr = conditions.get(0).getSecond().length(); final int np = 7; BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); System.out.println("Please answer the following questions with a y or n:"); final boolean[] answers = new boolean[nc]; for (int c = 0; c < nc; ++c) { String input; do { System.out.printf(" %s ? ", conditions.get(c).getFirst()); input = br.readLine().toUpperCase(); } while (!Objects.equals(input, "Y") && !Objects.equals(input, "N")); answers[c] = Objects.equals(input, "Y"); } System.out.println("\nRecommended action(s)"); outer: for (int r = 0; r < nr; ++r) { for (int c = 0; c < nc; ++c) { char yn = answers[c] ? 'Y' : 'N'; if (conditions.get(c).getSecond().charAt(r) != yn) { continue outer; } } if (r == np) { System.out.println(" None (no problem detected)"); } else { for (Pair<String, String> action : actions) { if (action.getSecond().charAt(r) == 'Y') { System.out.printf(" %s\n", action.getFirst()); } } } break; } } }  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 ## 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[0].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;
$('input:checkbox:checked').each(function () { sum += Number(this.value); }); // Translate sum into an index (column #) into bools. var index = questions[0].bools.length - sum - 1; // Clear the answers.$('#ul').html('');

for (var i = 0; i < answers.length; i++) {
$('#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.js Printer prints [Y/N]?Y A red light is flashing [Y/N]?Y Printer is recognized by computer [Y/N]?Y Check/replace ink.  ## jq Translation of: Wren Works with: jq Works with gojq, the Go implementation of jq In the following solution, input is used to read the user's yes/no responses, and so jq should be invoked with the -R and -n command-line options. Because of the limitations of jq's I/O capabilities, the prompts for this task are written to stderr, which unfortunately makes them untidy. def get_response: input | if . == "Y" or . == "y" then "Y" elif . == "N" or . == "n" then "N" else null end; def ask($prompt):
$prompt|stderr | get_response | if . then . else ask end; ask; def conditions: [ ["Printer prints" , "NNNNYYYY"], ["A red light is flashing" , "YYNNYYNN"], ["Printer is recognized by computer", "NYNYNYNY"] ]; def actions: [ ["Check the power cable" , "NNYNNNNN"], ["Check the printer-computer cable" , "YNYNNNNN"], ["Ensure printer software is installed", "YNYNYNYN"], ["Check/replace ink" , "YYNNNYNN"], ["Check for paper jam" , "NYNYNNNN"] ]; def interact: conditions as$conditions
| actions as $actions | ($conditions|length) as $nc | ($actions|length) as $na | ($conditions[0][1]|length) as $nr # number of rules | 7 as$np                           # index of 'no problem' rule
( reduce range(0; $nc) as$c ( null;
.[$c] = ask("\($conditions[$c][0])? ") )) as$answers
| ("\nRecommended action(s):",
label $out | range(0;$nr) as $r | if all( range(0;$nc); $conditions[.][1][$r:$r+1] ==$answers[.])
then if $r ==$np
then "None (no problem detected)."
else $actions[] | select(.[1][$r:$r+1] == "Y") | .[0] end, break$out
else empty
end ) ;

interact

Example (transcript)

$jq -rRn -f decision-tables.jq 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  ## 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()))[1]) in ['Y', 'N'] return ans end end end 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 end end 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[0].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} ? ")
}
while (input != "Y" && input != "N")
}
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  ## Lua Translation of: C++ function promptYN(q) local ans = '?' repeat io.write(q..'? ') ans = string.upper(io.read()) until ans == 'Y' or ans == 'N' return ans == 'Y' end function getCharAt(s,i) return string.sub(s,i,i) end conditions = { {"Printer prints", "NNNNYYYY"}, {"A red light is flashing", "YYNNYYNN"}, {"Printer is recognized by computer", "NYNYNYNY"}, } actions = { {"Check the power cable", "NNYNNNNN"}, {"Check the printer-computer cable", "YNYNNNNN"}, {"Ensure printer software is installed", "YNYNYNYN"}, {"Check/replace ink", "YYNNNYNN"}, {"Check for paper jam", "NYNYNNNN"}, } nc = #conditions nr = string.len(conditions[1][2]) answers = {} print('Please answer the following questions with a y or n:') for i,v in pairs(conditions) do answers[i] = promptYN(v[1]) end print('Recommended action(s)') for r=1,nr do local skip = false for c=1,nc do local yn = answers[c] and 'Y' or 'N' if getCharAt(conditions[c][2], r) ~= yn then skip = true break end end if not skip then if r == nr then print(" None (no problem detected)") else for i,a in pairs(actions) do if getCharAt(a[2], r) == 'Y' then print(" ", a[1]) end end end end end  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 ## Nim We have defined a generic decision table object and used it with the Wikipedia printer example. import strutils, tables #################################################################################################### # Generic defintion of the decision table. type DTable[Cond, Act: Ordinal] = object questions: array[Cond, string] answers: array[Act, string] rules: Table[set[Cond], seq[Act]] proc initDTable[Cond, Act](): DTable[Cond, Act] = discard proc addCondition[Cond, Act](dt: var DTable[Cond, Act]; cond: Cond; question: string) = if dt.questions[cond].len != 0: raise newException(ValueError, "condition already set: " &$cond)
dt.questions[cond] = question

raise newException(ValueError, "action already set: " & $act) dt.answers[act] = answer proc addRule[Cond, Act](dt: var DTable[Cond, Act]; rule: set[Cond]; acts: openArray[Act]) = if rule in dt.rules: raise newException(ValueError, "rule already set.") dt.rules[rule] = @acts proc askQuestion(question: string): string = while true: stdout.write question & ' ' stdout.flushFile() result = stdin.readLine().strip() if result in ["y", "n"]: break proc apply[Cond, Act](dt: DTable[Cond, Act]) = # Build condition set. var conds: set[Cond] echo "Answer questions with 'y' or 'n'" for cond, question in dt.questions: if question.len == 0: raise newException(ValueError, "missing question for condition: " &$cond)
conds.incl cond

# Apply rule.
echo()
if conds in dt.rules:
echo "Actions recommended:"
for act in dt.rules[conds]:
else:
echo "No action recommended."

####################################################################################################
# Decision table for Wikipedia printer example.

type

Condition {.pure.} = enum PrinterPrints, RedLightFlashing, PrinterRecognized
Action {.pure.} = enum CheckPowerCable, CheckPrinterCable, CheckSoftware, CheckInk, CheckPaperJam

const

Questions = [PrinterPrints:     "Does printer print?",
RedLightFlashing:  "Does red light is flashing?",
PrinterRecognized: "Is printer recognized by computer?"]

Answers = [CheckPowerCable:   "check the power cable",
CheckPrinterCable: "check the printer-computer cable",
CheckSoftware:     "ensure printer software is installed",
CheckInk:          "check/replace ink",
CheckPaperJam:     "check for paper jam"]

var dt = initDTable[Condition, Action]()

for cond, question in Questions:

dt.apply()

Output:
Answer questions with 'y' or 'n'
Does printer print? n
Does red light is flashing? y
Is printer recognized by computer? y

Actions recommended:
- check/replace ink
- check for paper jam

## Perl

use v5.36;

sub decide($q,$a) {
my @q = @{$q}; my %a = %{$a};
my($cnt,$bit) = (1,0);

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',
);

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',
);


Output:
Printer is unrecognised: n
A red light is flashing: n
Printer does not print: y
Check for paper jam

## 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.

### console version

without js -- (wait_key)
constant conditions = """
YYYYNNNN:Printer does not print
YYNNYYNN:A red light is flashing
YNYNYNYN:Printer is unrecognized
"""
constant actions = """
--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
"""

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 for
end procedure

constant qa = split_any(conditions,"\n:"),
sa = split_any(actions,"\n:")
integer l = length(qa[1])

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
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 valid
end function

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
end procedure

procedure main()
try
validate(qa,l,"YN","condition")
validate(sa,l,"-X","action")
catch e
?e
abort(0)
end try
integer sv = sum(valid)
if sv=0 then
elsif sv=1 then
else
for i=1 to length(valid) do
if valid[i] then
printf(1,"for %d:\n",i)
end if
end for
end if
end procedure
main()

Output:
Printer does not print:? N
A red light is flashing:? Y
Printer is unrecognized:? Y
Ensure printer software is installed
Check/replace ink


### GUI version

Library: Phix/pGUI
with javascript_semantics
constant conditions = """
YYYYNNNN:Printer does not print
YYNNYYNN:A red light is flashing
YNYNYNYN:Printer is unrecognized
"""
constant actions = """
--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
"""

constant {qyn,qus} = columnize(apply(true,split,{split(conditions,'\n'),':'})),
{a_x,act} = columnize(apply(true,split,{split(actions,'\n'),':'}))
integer nq = length(qus), na = length(act), ynl = length(qyn[1])
assert(apply(qyn,length)=repeat(ynl,nq),"mismatched YN lengths")
assert(apply(a_x,length)=repeat(ynl,na),"mismatched X- lengths")
assert(unique(join(qyn,""))="NY" and unique(join(a_x,""))="-X")

constant title = "Decision_tables",
help_text = """
Check all that apply and press the "Get Answers" button.
"""
include pGUI.e
Ihandle dlg, tbox, hbox, vbox, okbtn, answers
sequence toggles

function show_help()
IupMessage(title,help_text)
return IUP_IGNORE -- (don't open browser help!)
end function

function button_cb(Ihandle /*okbtn*/)
sequence valid = repeat(true,ynl)
for i=1 to nq do
integer yn = "YN"[2-IupGetInt(toggles[i],"VALUE")]
for j=1 to ynl do
if yn!=qyn[i][j] then valid[j] = false end if
end for
end for
integer sv = sum(valid)
if sv!=0 then
for i=1 to ynl do
if valid[i] then
if sv>1 then
end if
sequence actions = {}
for j=1 to na do
if a_x[j][i]='X' then
actions = append(actions,act[j])
end if
end for
end if
end for
end if
IupSetAttribute(dlg,"SIZE",NULL)
IupRefresh(dlg)
return IUP_DEFAULT
end function

function key_cb(Ihandle /*dlg*/, atom c)
if c=K_ESC then return IUP_CLOSE end if -- (standard practice for me)
if c=K_F5 then return IUP_DEFAULT end if -- (let browser reload work)
if c=K_F1 then return show_help() end if
if c=K_CR then return button_cb(okbtn) end if
return IUP_IGNORE
end function

IupOpen()
toggles = apply(true,IupToggle,{qus,{"RIGHTBUTTON=YES, CANFOCUS=NO"}})
tbox = IupVbox(toggles,"ALIGNMENT=ARIGHT")
hbox = IupHbox({tbox,IupVbox({IupLabel(),okbtn})})
dlg = IupDialog(vbox,TITLE="%s", MINSIZE=540x200,{title})
IupShow(dlg)
IupSetCallback(dlg,"KEY_CB",Icallback("key_cb"))
IupSetAttributeHandle(NULL,"PARENTDIALOG",dlg)
if platform()!=JS then
IupMainLoop()
IupClose()
end if


## Picat

### Interactive version

import util.
%
% Interactive version.
%
go =>
conditions(Conditions),
solutions(Solutions),

nl.

%
% Query the user about the problem.
% Valid responses: YyNn
%
Answers = [0 : _I in 1..Conditions[1,2].length],
foreach([Text,Cond] in Conditions)
A = "",
while (not(membchk(A, ["Y","N","y","n"])))
printf("%s? ", Text),
if membchk(A,["Y","y"]) then
end
end
end,
nl.

%
% Get the result given the answers (list of 01).
%
Result = [],
Result := ["Nice, no problem."]
else
foreach([Text,Sol] in Solutions)
Result := Result ++ [Text]
end
end
end.

conditions(Conditions) =>
Conditions = [
["Printer does not print",		[1,1,1,1,0,0,0,0]],
["A red light is flashing",		[1,1,0,0,1,1,0,0]],
["Printer is unrecognised",		[1,0,1,0,1,0,1,0]]
].

solutions(Solutions) =>
Solutions = [
["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]]
].
Output:
Please answer the questions with YyNn.
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
Check for paper jam

For debugging purposes it it's nice to be able to print all the possible combinations of answers/solutions.

%
% Go through all combinations of answers
%
go2 =>
PS = power_set([1,2,3]).delete([]).sort(),
println(PS),
conditions(Conditions),
solutions(Solutions),
AllCond = [Cond : [_,Cond] in Conditions],
foreach(P in PS)
println(p=P),
println(conditions=join([Conditions[I].first() : I in P],', ')),
A = [0:_I in 1..Conditions[1,2].length],
foreach(C in [AllCond[I] : I in P])
A := map(\/,A,C)
end,
println(a=A),
println(join(decision_table(Solutions,A),'\n')),

nl
end,
nl.
Output:

(truncated)

p = [1]
conditions = Printer does not print
a = [1,1,1,1,0,0,0,0]
Check the power cable
Check the printer-computer cable
Check for paper jam

p = [1,2]
conditions = Printer does not print, A red light is flashing
a = [1,1,1,1,1,1,0,0]
Check the power cable
Check the printer-computer cable
Check/replace ink
Check for paper jam

p = [1,2,3]
conditions = Printer does not print, A red light is flashing, Printer is unrecognised
a = [1,1,1,1,1,1,1,0]
Check the power cable
Check the printer-computer cable
Ensure printer software is installed
Check/replace ink
Check for paper jam

...


## PicoLisp

We allow ourselves a luxurious user interface:

(de yes? (Cond)
(out NIL (prin (car Cond) "? "))
(in NIL
(loop
(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 ()
(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[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)


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!

## Quackery

  [ say "Check power cable." cr ]                  is cpc       (   -->   )
[ say "Check printer-computer cable." cr ]       is cpcc      (   -->   )
[ say "Ensure printer software installed." cr ]  is epsi      (   -->   )
[ say "Check/replace ink." cr ]                  is cri       (   -->   )
[ say "Check for paper jam." cr ]                is cpj       (   -->   )
[ say "No problem detected." cr ]                is npd       (   -->   )

[ [ dup $" (y/n) " join input dup$ "" = iff drop again ]
nip 0 peek upper char Y = ]                  is condition ( $--> b ) [$ "Does the printer print?"
condition
$"Is a red light flashing?" condition$ "Does the computer recognise the printer?"
condition
1 << | 1 << |
[ table
( n n n ) [ cpc cpcc epsi ]
( y n n ) epsi
( n y n ) [ cpcc epsi cri ]
( y y n ) epsi
( n n y ) cpj
( y n y ) npd
( n y y ) [ cri cpj ]
( y y y ) cri ]
cr do ]                                        is diagnose  (   -->   )
Output:

As a dialogue in the Quackery shell.

/O> diagnose
...
Does the printer print? (y/n) n
Is a red light flashing? (y/n) n
Does the computer recognise the printer? (y/n) y

Check for paper jam.



## 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

(printf "~a [y/n]?" q)
(define (get-y/n)
[(? eof-object?) eof]
[(regexp #rx"^[yY]") #t]
[(regexp #rx"^[nN]") #f]
(get-y/n))

(define (cells->hash grid)
(for*/hash ((block (in-list grid)) (address (in-list (car 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)

## Raku

(formerly 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 ## REXX This REXX example shows how one version of a decision table could be implemented, There was additional support added to the code for: • 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 = 3 /*the number of questions to be asked. */ action.= /* 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 while Q.i\==''; ans.i= asker(i) /*display the question, obtain response*/ end /*i*/ 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 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 '═════════ There are no solutions 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 some of the possible responses): (decision.rex is the name of the REXX program that produced this output.) D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? no ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? No ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? n ◄■■■■■■■■ user input. ═════════ There are no solutions for the information supplied. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? n ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? n ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? yes ◄■■■■■■■■ user input. ═════════ Ensure printer software is installed. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? n ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? Ye ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? n ◄■■■■■■■■ user input. ═════════ Check/replace ink. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? n ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? yes. ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? yes ◄■■■■■■■■ user input. ═════════ Ensure printer software is installed. ═════════ Check/replace ink. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? y ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? no ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? no ◄■■■■■■■■ user input. ═════════ Check for paper jam. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? y ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? n ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? y ◄■■■■■■■■ user input. ═════════ 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 ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? y ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? n ◄■■■■■■■■ user input. ═════════ Check/replace ink. ═════════ Check for paper jam. D:\►rexx decision ───────── (question 1 of 3) Does the printer not print? y ◄■■■■■■■■ user input. ───────── (question 2 of 3) Is there a red light flashing on the printer? y ◄■■■■■■■■ user input. ───────── (question 3 of 3) Is the printer unrecognized by the software? y ◄■■■■■■■■ user input. ═════════ 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 notprinting see "A red light is upper(flashing) (Y or N) " give flashing see "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" + nl elseif 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" + nl elseif upper(notprinting) = "Y" and upper(flashing) = "N" and upper(notrecognized) = "N" see "Check for paper jam" + nl elseif upper(notprinting) = "N" and upper(flashing) = "Y" and upper(notrecognized) = "Y" see "Ensure printer software is installed" + nl see "Check/replace ink" + nl elseif upper(notprinting) = "N" and upper(flashing) = "Y" and upper(notrecognized) = "N" see "Check/replace ink" + nl elseif upper(notprinting) = "N" and upper(flashing) = "N" and upper(notrecognized) = "Y" see "Ensure printer software is installed" + nl elseif upper(notprinting) = "N" and upper(flashing) = "N" and upper(notrecognized) = "N" see "no action found" + nl else see "invalid input: " + upper(notprinting) + " " + upper(flashing) + " " + upper(notrecognized) + nl ok 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 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}  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: PC LOAD LETTER ## Scala Translation of: Java import java.io.{BufferedReader, InputStreamReader} import scala.util.control.Breaks object DecisionTables { val conditions = List( ("Printer prints", "NNNNYYYY"), ("A red light is flashing", "YYNNYYNN"), ("Printer is recognized by computer", "NYNYNYNY") ) val actions = List( ("Check the power cable", "NNYNNNNN"), ("Check the printer-computer cable", "YNYNNNNN"), ("Ensure printer software is installed", "YNYNYNYN"), ("Check/replace ink", "YYNNNYNN"), ("Check for paper jam", "NYNYNNNN") ) def main(args: Array[String]): Unit = { // var x = (1, 2) // println(x) // println(conditions) // println(actions) val nc = conditions.size val na = actions.size val nr = conditions.head._2.length val np = 7 val br = new BufferedReader(new InputStreamReader(System.in)) println("Please answer the following questions with a y or n:") val answers = Array.ofDim[Boolean](nc) for (c <- 0 until nc) { var input = "" do { printf(" %s ? ", conditions(c)._1) input = br.readLine().toUpperCase } while (input != "Y" && input != "N") answers(c) = input == "Y" } println("\nRecommended actions(s)") val Outer = new Breaks val Inner = new Breaks Outer.breakable { for (r <- 0 until nr) { var outer = true Inner.breakable { for (c <- 0 until nc) { val yn = if (answers(c)) 'Y' else 'N' if (conditions(c)._2(r) != yn) { outer = false Inner.break } } } if (outer) { if (r == np) { println(" None (no problem detected)") } else { for (action <- actions) { if (action._2(r) == 'Y') { printf(" %s\n", action._1) } } } Outer.break } } } } }  Output: Please answer the following questions with a y or n: Printer prints ? y A red light is flashing ? y Printer is recognized by computer ? y Recommended actions(s) Check/replace ink ## Sidef Translation of: Raku 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#Tcl proc 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


## Wren

Translation of: Kotlin
Library: Wren-str
import "io" for Stdin, Stdout
import "./str" for Str

var conditions = [
["Printer prints"                   , "NNNNYYYY"],
["A red light is flashing"          , "YYNNYYNN"],
["Printer is recognized by computer", "NYNYNYNY"]
]

var actions = [
["Check the power cable"               , "NNYNNNNN"],
["Check the printer-computer cable"    , "YNYNNNNN"],
["Ensure printer software is installed", "YNYNYNYN"],
["Check/replace ink"                   , "YYNNNYNN"],
["Check for paper jam"                 , "NYNYNNNN"]
]

var nc = conditions.count
var na = actions.count
var nr = conditions[0][1].count  // number of rules
var np = 7  // index of 'no problem' rule
for (c in 0...nc) {
var input
while (true) {
System.write("  %(conditions[c][0]) ? ")
Stdout.flush()
if (input == "Y" || input == "N") break
}
}
System.print("\nRecommended action(s):")
for (r in 0...nr) {
var outer = false
for (c in 0...nc) {
var yn = answers[c] ? "Y" : "N"
if (conditions[c][1][r] != yn) {
outer = true
break
}
}
if (!outer) {
if (r == np) {
System.print("  None (no problem detected)")
} else {
for (a in 0...na) {
if (actions[a][1][r] == "Y") System.print("  %(actions[a][0])")
}
}
break
}
}

Output:

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


## XPL0

Translation of: Wren
include xpllib; \for ToUpper, Print

int  Conditions, Actions, NC, NA, NR, NP, Answers(3), Input, Outer, YN, R, C, A;
char S;
[Conditions:= [
["Printer prints"                   , "NNNNYYYY"],
["A red light is flashing"          , "YYNNYYNN"],
["Printer is recognized by computer", "NYNYNYNY"]
];
Actions:= [
["Check the power cable"               , "NNYNNNNN"],
["Check the printer-computer cable"    , "YNYNNNNN"],
["Ensure printer software is installed", "YNYNYNYN"],
["Check/replace ink"                   , "YYNNNYNN"],
["Check for paper jam"                 , "NYNYNNNN"]
];
NC:= 3;
NA:= 5;
NR:= 8;         \number of rules
NP:= 7;         \index of 'no problem' rule
for C:= 0 to NC-1 do
[loop   [Print("  %s ? ", Conditions(C,0));
OpenI(0);
Input:= ToUpper(ChIn(0));
if Input = ^Y or Input = ^N then quit;
];
];
Print("\nRecommended action(s):\n");
for R:= 0 to NR-1 do
[Outer:= false;
for C:= 0 to NC-1 do
[YN:= if Answers(C) then ^Y else ^N;
S:= Conditions(C,1);    \to access character bytes not integers
if S(R) # YN then
[Outer:= true;
C:= NC;         \break
];
];
if not Outer then
[if R = NP then
Print("  None (no problem detected)\n")
else    [for A:= 0 to NA-1 do
[S:= Actions(A,1);
if S(R) = ^Y then
Print("  %s\n", Actions(A,0));
];
];
R:= NR;                 \break
];
];
]
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
`