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I'm sorting strings that are comprised of text and numbers.
I want the sort to sort the number parts as numbers, not alphanumeric.
For example I want: abc1def, ..., abc9def, abc10def
instead of: abc10def, abc1def, ..., abc9def
Does anyone know an algorithm for this (in particular in c++)
Thanks
I asked this exact question (although in Java) and got pointed to http://www.davekoelle.com/alphanum.html which has an algorithm and implementations of it in many languages.
Update 14 years later: Dave Koelle’s blog has gone off line and I can’t find his actual algorithm, but here’s an implementation.
https://github.com/cblanc/koelle-sort
Several natural sort implementations for C++ are available. A brief review:
natural_sort<> - based on Boost.Regex.
In my tests, it's roughly 20 times slower than other options.
Dirk Jagdmann's alnum.hpp, based on Dave Koelle's alphanum algorithm
Potential integer overlow issues for values over MAXINT
Martin Pool's natsort - written in C, but trivially usable from C++.
The only C/C++ implementation I've seen to offer a case insensitive version, which would seem to be a high priority for a "natural" sort.
Like the other implementations, it doesn't actually parse decimal points, but it does special case leading zeroes (anything with a leading 0 is assumed to be a fraction), which is a little weird but potentially useful.
PHP uses this algorithm.
This is known as natural sorting. There's an algorithm here that looks promising.
Be careful of problems with non-ASCII characters (see Jeff's blog entry on the subject).
Partially reposting my another answer:
bool compareNat(const std::string& a, const std::string& b){
if (a.empty())
return true;
if (b.empty())
return false;
if (std::isdigit(a[0]) && !std::isdigit(b[0]))
return true;
if (!std::isdigit(a[0]) && std::isdigit(b[0]))
return false;
if (!std::isdigit(a[0]) && !std::isdigit(b[0]))
{
if (a[0] == b[0])
return compareNat(a.substr(1), b.substr(1));
return (toUpper(a) < toUpper(b));
//toUpper() is a function to convert a std::string to uppercase.
}
// Both strings begin with digit --> parse both numbers
std::istringstream issa(a);
std::istringstream issb(b);
int ia, ib;
issa >> ia;
issb >> ib;
if (ia != ib)
return ia < ib;
// Numbers are the same --> remove numbers and recurse
std::string anew, bnew;
std::getline(issa, anew);
std::getline(issb, bnew);
return (compareNat(anew, bnew));
}
toUpper() function:
std::string toUpper(std::string s){
for(int i=0;i<(int)s.length();i++){s[i]=toupper(s[i]);}
return s;
}
Usage:
std::vector<std::string> str;
str.push_back("abc1def");
str.push_back("abc10def");
...
std::sort(str.begin(), str.end(), compareNat);
To solve what is essentially a parsing problem a state machine (aka finite state automaton) is the way to go. Dissatisfied with the above solutions i wrote a simple one-pass early bail-out algorithm that beats C/C++ variants suggested above in terms of performance, does not suffer from numerical datatype overflow errors, and is easy to modify to add case insensitivity if required.
sources can be found here
For those that arrive here and are already using Qt in their project, you can use the QCollator class. See this question for details.
Avalanchesort is a recursive variation of naturall sort, whiche merge runs, while exploring the stack of sorting-datas. The algorithim will sort stable, even if you add datas to your sorting-heap, while the algorithm is running/sorting.
The search-principle is simple. Only merge runs with the same rank.
After finding the first two naturell runs (rank 0), avalanchesort merge them to a run with rank 1. Then it call avalanchesort, to generate a second run with rank 1 and merge the two runs to a run with rank 2. Then it call the avalancheSort to generate a run with rank 2 on the unsorted datas....
My Implementation porthd/avalanchesort divide the sorting from the handling of the data using interface injection. You can use the algorithmn for datastructures like array, associative arrays or lists.
/**
* #param DataListAvalancheSortInterface $dataList
* #param DataRangeInterface $beginRange
* #param int $avalancheIndex
* #return bool
*/
public function startAvalancheSort(DataListAvalancheSortInterface $dataList)
{
$avalancheIndex = 0;
$rangeResult = $this->avalancheSort($dataList, $dataList->getFirstIdent(), $avalancheIndex);
if (!$dataList->isLastIdent($rangeResult->getStop())) {
do {
$avalancheIndex++;
$lastIdent = $rangeResult->getStop();
if ($dataList->isLastIdent($lastIdent)) {
$rangeResult = new $this->rangeClass();
$rangeResult->setStart($dataList->getFirstIdent());
$rangeResult->setStop($dataList->getLastIdent());
break;
}
$nextIdent = $dataList->getNextIdent($lastIdent);
$rangeFollow = $this->avalancheSort($dataList, $nextIdent, $avalancheIndex);
$rangeResult = $this->mergeAvalanche($dataList, $rangeResult, $rangeFollow);
} while (true);
}
return $rangeResult;
}
/**
* #param DataListAvalancheSortInterface $dataList
* #param DataRangeInterface $range
* #return DataRangeInterface
*/
protected function findRun(DataListAvalancheSortInterface $dataList,
$startIdent)
{
$result = new $this->rangeClass();
$result->setStart($startIdent);
$result->setStop($startIdent);
do {
if ($dataList->isLastIdent($result->getStop())) {
break;
}
$nextIdent = $dataList->getNextIdent($result->getStop());
if ($dataList->oddLowerEqualThanEven(
$dataList->getDataItem($result->getStop()),
$dataList->getDataItem($nextIdent)
)) {
$result->setStop($nextIdent);
} else {
break;
}
} while (true);
return $result;
}
/**
* #param DataListAvalancheSortInterface $dataList
* #param $beginIdent
* #param int $avalancheIndex
* #return DataRangeInterface|mixed
*/
protected function avalancheSort(DataListAvalancheSortInterface $dataList,
$beginIdent,
int $avalancheIndex = 0)
{
if ($avalancheIndex === 0) {
$rangeFirst = $this->findRun($dataList, $beginIdent);
if ($dataList->isLastIdent($rangeFirst->getStop())) {
// it is the last run
$rangeResult = $rangeFirst;
} else {
$nextIdent = $dataList->getNextIdent($rangeFirst->getStop());
$rangeSecond = $this->findRun($dataList, $nextIdent);
$rangeResult = $this->mergeAvalanche($dataList, $rangeFirst, $rangeSecond);
}
} else {
$rangeFirst = $this->avalancheSort($dataList,
$beginIdent,
($avalancheIndex - 1)
);
if ($dataList->isLastIdent($rangeFirst->getStop())) {
$rangeResult = $rangeFirst;
} else {
$nextIdent = $dataList->getNextIdent($rangeFirst->getStop());
$rangeSecond = $this->avalancheSort($dataList,
$nextIdent,
($avalancheIndex - 1)
);
$rangeResult = $this->mergeAvalanche($dataList, $rangeFirst, $rangeSecond);
}
}
return $rangeResult;
}
protected function mergeAvalanche(DataListAvalancheSortInterface $dataList, $oddListRange, $evenListRange)
{
$resultRange = new $this->rangeClass();
$oddNextIdent = $oddListRange->getStart();
$oddStopIdent = $oddListRange->getStop();
$evenNextIdent = $evenListRange->getStart();
$evenStopIdent = $evenListRange->getStop();
$dataList->initNewListPart($oddListRange, $evenListRange);
do {
if ($dataList->oddLowerEqualThanEven(
$dataList->getDataItem($oddNextIdent),
$dataList->getDataItem($evenNextIdent)
)) {
$dataList->addListPart($oddNextIdent);
if ($oddNextIdent === $oddStopIdent) {
$restTail = $evenNextIdent;
$stopTail = $evenStopIdent;
break;
}
$oddNextIdent = $dataList->getNextIdent($oddNextIdent);
} else {
$dataList->addListPart($evenNextIdent);
if ($evenNextIdent === $evenStopIdent) {
$restTail = $oddNextIdent;
$stopTail = $oddStopIdent;
break;
}
$evenNextIdent = $dataList->getNextIdent($evenNextIdent);
}
} while (true);
while ($stopTail !== $restTail) {
$dataList->addListPart($restTail);
$restTail = $dataList->getNextIdent($restTail);
}
$dataList->addListPart($restTail);
$dataList->cascadeDataListChange($resultRange);
return $resultRange;
}
}
My algorithm with test code of java version. If you want to use it in your project you can define a comparator yourself.
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.function.Consumer;
public class FileNameSortTest {
private static List<String> names = Arrays.asList(
"A__01__02",
"A__2__02",
"A__1__23",
"A__11__23",
"A__3++++",
"B__1__02",
"B__22_13",
"1_22_2222",
"12_222_222",
"2222222222",
"1.sadasdsadsa",
"11.asdasdasdasdasd",
"2.sadsadasdsad",
"22.sadasdasdsadsa",
"3.asdasdsadsadsa",
"adsadsadsasd1",
"adsadsadsasd10",
"adsadsadsasd3",
"adsadsadsasd02"
);
public static void main(String...args) {
List<File> files = new ArrayList<>();
names.forEach(s -> {
File f = new File(s);
try {
if (!f.exists()) {
f.createNewFile();
}
files.add(f);
} catch (IOException e) {
e.printStackTrace();
}
});
files.sort(Comparator.comparing(File::getName));
files.forEach(f -> System.out.print(f.getName() + " "));
System.out.println();
files.sort(new Comparator<File>() {
boolean caseSensitive = false;
int SPAN_OF_CASES = 'a' - 'A';
#Override
public int compare(File left, File right) {
char[] csLeft = left.getName().toCharArray(), csRight = right.getName().toCharArray();
boolean isNumberRegion = false;
int diff=0, i=0, j=0, lenLeft=csLeft.length, lenRight=csRight.length;
char cLeft = 0, cRight = 0;
for (; i<lenLeft && j<lenRight; i++, j++) {
cLeft = getCharByCaseSensitive(csLeft[i]);
cRight = getCharByCaseSensitive(csRight[j]);
boolean isNumericLeft = isNumeric(cLeft), isNumericRight = isNumeric(cRight);
if (isNumericLeft && isNumericRight) {
// Number start!
if (!isNumberRegion) {
isNumberRegion = true;
// Remove prefix '0'
while (i < lenLeft && cLeft == '0') i++;
while (j < lenRight && cRight == '0') j++;
if (i == lenLeft || j == lenRight) break;
}
// Diff start: calculate the diff value.
if (cLeft != cRight && diff == 0)
diff = cLeft - cRight;
} else {
if (isNumericLeft != isNumericRight) {
// One numeric and one char.
if (isNumberRegion)
return isNumericLeft ? 1 : -1;
return cLeft - cRight;
} else {
// Two chars: if (number) diff don't equal 0 return it.
if (diff != 0)
return diff;
// Calculate chars diff.
diff = cLeft - cRight;
if (diff != 0)
return diff;
// Reset!
isNumberRegion = false;
diff = 0;
}
}
}
// The longer one will be put backwards.
return (i == lenLeft && j == lenRight) ? cLeft - cRight : (i == lenLeft ? -1 : 1) ;
}
private boolean isNumeric(char c) {
return c >= '0' && c <= '9';
}
private char getCharByCaseSensitive(char c) {
return caseSensitive ? c : (c >= 'A' && c <= 'Z' ? (char) (c + SPAN_OF_CASES) : c);
}
});
files.forEach(f -> System.out.print(f.getName() + " "));
}
}
The output is,
1.sadasdsadsa 11.asdasdasdasdasd 12_222_222 1_22_2222 2.sadsadasdsad 22.sadasdasdsadsa 2222222222 3.asdasdsadsadsa A__01__02 A__11__23 A__1__23 A__2__02 A__3++++ B__1__02 B__22_13 adsadsadsasd02 adsadsadsasd1 adsadsadsasd10 adsadsadsasd3
1.sadasdsadsa 1_22_2222 2.sadsadasdsad 3.asdasdsadsadsa 11.asdasdasdasdasd 12_222_222 22.sadasdasdsadsa 2222222222 A__01__02 A__1__23 A__2__02 A__3++++ A__11__23 adsadsadsasd02 adsadsadsasd1 adsadsadsasd3 adsadsadsasd10 B__1__02 B__22_13
Process finished with exit code 0
// -1: s0 < s1; 0: s0 == s1; 1: s0 > s1
static int numericCompare(const string &s0, const string &s1) {
size_t i = 0, j = 0;
for (; i < s0.size() && j < s1.size();) {
string t0(1, s0[i++]);
while (i < s0.size() && !(isdigit(t0[0]) ^ isdigit(s0[i]))) {
t0.push_back(s0[i++]);
}
string t1(1, s1[j++]);
while (j < s1.size() && !(isdigit(t1[0]) ^ isdigit(s1[j]))) {
t1.push_back(s1[j++]);
}
if (isdigit(t0[0]) && isdigit(t1[0])) {
size_t p0 = t0.find_first_not_of('0');
size_t p1 = t1.find_first_not_of('0');
t0 = p0 == string::npos ? "" : t0.substr(p0);
t1 = p1 == string::npos ? "" : t1.substr(p1);
if (t0.size() != t1.size()) {
return t0.size() < t1.size() ? -1 : 1;
}
}
if (t0 != t1) {
return t0 < t1 ? -1 : 1;
}
}
return i == s0.size() && j == s1.size() ? 0 : i != s0.size() ? 1 : -1;
}
I am not very sure if it is you want, anyway, you can have a try:-)
I am using Seive method to calculate prime numbers up to a limit (say 100).
I constructed a List<bool> to hold if an index (which will eventually be the number) is prime or not. This part is fine.
Finally, I need return the numbers (index). Now I am using:
for(var i=2;i<=max;i++) {
if(!is_composite[i]){
primes.add(i);
}
}
return primes;
This will give the correct list containing only the prime numbers.
I am wondering if I can do a filter on is_composite and returns the "index" associated?
As requested, the complete code:
List<int> findPrimes(int max) {
var is_composite=List<bool>(max+1);
var primes=List<int>();
is_composite.fillRange(0, max, false);
for(var i=4;i<=max;i+=2) {
is_composite[i]=true;
}
var next_prime=3;
var stop=sqrt(max);
while(next_prime<=stop) {
for(var i=next_prime*2;i<=max;i+=next_prime) {
is_composite[i]=true;
}
next_prime+=2;
while(next_prime<=max && is_composite[next_prime]) {
next_prime+=2;
}
}
// TODO: is there a beter way instead of iterating the list?
for(var i=2;i<=max;i++) {
if(!is_composite[i]){
primes.add(i);
}
}
return primes;
}
For the given algorithm you could properly reorder some stuff to make it easier to get the result by changing your is_composite list of boolean into a is_not_composite list of integers which are closer to what your want to return as the result:
List<int> findPrimes(int max) {
final is_not_composite = List.generate(max + 1, (i) => i);
for (var i = 4; i <= max; i += 2) {
is_not_composite.remove(i);
}
var next_prime = 3;
final stop = sqrt(max);
while (next_prime <= stop) {
for (var i = next_prime * 2; i <= max; i += next_prime) {
is_not_composite.remove(i);
}
next_prime += 2;
while (next_prime <= max && !is_not_composite.contains(next_prime)) {
next_prime += 2;
}
}
return is_not_composite.sublist(2);
}
I wrote the following code to look through the last 100 candlesticks and draw a rectangle around a bullish engulfing candlestick patterns. I hope extend it for bearish engulfing pattern too. I don't know why, but the rectangles don't draw. Please take a look at the code below
bool isBullishEngulfing(int current) {
if((iClose(_Symbol,0,current) > iOpen(_Symbol,0,current)) && (iClose(_Symbol,0,current + 1) < iOpen(_Symbol,0,current + 1)) &&
(iOpen(_Symbol,0,current) < iClose(_Symbol,0,current + 1)) && (iClose(_Symbol,0,current) > iOpen(_Symbol,0,current + 1)))
return true;
return false;
}
void showRectangles() {
for (int i=100;i<=1;i--) {
if(isBullishEngulfing(i)) {
drawBullRectangle(i,iHigh(_Symbol,0,i),iLow(_Symbol,0,i));
}
}
}
bool drawBullRectangle(int candleInt,const double top,const double bottom)
{
const datetime starts=iTime(_Symbol,0,candleInt);
const datetime ends=starts+PeriodSeconds()*Numbars; //Numbars shows how long the rectangle should draw
const string name=prefix+"_"+(candleInt>0?"DEMAND":"SUPPLY")+"_"+TimeToString(starts);
if(!ObjectCreate(0,name,OBJ_RECTANGLE,0,0,0,0,0))
{
printf("%i %s: failed to create %s. error=%d",__LINE__,__FILE__,name,_LastError);
return false;
}
ObjectSetInteger(0,name,OBJPROP_TIME1,starts);
ObjectSetInteger(0,name,OBJPROP_TIME2,ends);
ObjectSetDouble(0,name,OBJPROP_PRICE1,top);
ObjectSetDouble(0,name,OBJPROP_PRICE2,bottom);
ObjectSetInteger(0,name,OBJPROP_COLOR, clrAqua);
ObjectSetInteger(0,name,OBJPROP_STYLE, STYLE_SOLID);
ObjectSetInteger(0,name,OBJPROP_WIDTH,1);
ObjectSetInteger(0,name,OBJPROP_FILL, true);
return true;
}
void OnDeinit(const int reason){ObjectsDeleteAll(0,prefix);}
void OnTick()
{
if(!isNewBar())
return; //not necessary but waste of time to check every second
showRectangles();
}
bool isNewBar()
{
static datetime lastbar;
datetime curbar = (datetime)SeriesInfoInteger(_Symbol,_Period,SERIES_LASTBAR_DATE);
if(lastbar != curbar)
{
lastbar = curbar;
return true;
}
return false;
}
I would appreciate help to resolve this.
The error is mainly in the loop, it should be for (int i=100;i>=1;i--)
The other "possible" error is in the logic of theisBullishEngulfing() function.
Usually, the Close of the previous bar is equal to the Open of the current bar, so the following condition doesn't get fulfilled(most of the time)
iOpen(_Symbol,0,current) < iClose(_Symbol,0,current + 1)
(So, I suggest to remove this line, but this is just a suggestion, note there are occasions that your condition get fulfilled as well)
Some help with the following would be appreciated. I am writing some console test programs, and I want to be able to enter some parameters from the terminal (I don't want to use command line arguments - too many parameters). I have tried some variations, but I cannot find how to accomplish this. The following is the latest version of my test for terminal input. The problem with this program is that if an error is encountered, the Completer closes automatically, and I want to continue from either the Main() or from fGetNumber() function. While I can see why this program doesn't work, it illustrates what I need to achieve - re-enter the number, but I cannot find how to achieve that. If a valid number is entered, there is no problem. If an invalid number is entered, I cannot find out how to re-enter the number.
The code is as follows, and the problem I have is highlighted by "//////////" :
import "dart:async" as async;
import "dart:io";
void main() {
fGetNumber("Enter Nr of Iterations : ", 0, 999999)
.then((int iIters){
print ("In Main : Iterations selected = ${iIters}");
if (iIters == null) {
print ("In Main: Invalid Number of iterations : ${iIters}.");
} else {
fProcessData(iIters);
}
print ("Main Completed");
});
}
async.Future<int> fGetNumber(String sPrompt, int iMin, int iMax) {
print ("In fGetNumber");
int iIters = 0;
async.Completer<int> oCompleter = new async.Completer();
while (!oCompleter.isCompleted) { /////////// This loop does not work ///////
return fGetUserInput(sPrompt).then((String sIters) {
iIters = int.parse(sIters);
if (iIters < iMin || iIters > iMax) throw new Exception("Invalid");
oCompleter.complete(iIters);
return oCompleter.future;
}).catchError((_) => print ("Invalid - number must be from ${iMin} to ${iMax}")
).whenComplete(() => print ("fGetNumber - whenComplete"));// always gets here
}
print ("In fGetNumber (at end of function)"); //// it never gets here
}
async.Future<String> fGetUserInput(String sPrompt) {
print ("In fGetUserInput");
async.Completer<String> oCompleter = new async.Completer();
stdout.write(sPrompt);
async.Stream<String> oStream = stdin.transform(new StringDecoder());
async.StreamSubscription oSub;
oSub = oStream.listen((String sData) {
oCompleter.complete("$sData");
oSub.cancel();
});
return oCompleter.future;
}
void fProcessData(int iIters) {
print ("In fProcessData");
for (int iPos = 1; iPos <= iIters; iPos++ ) {
if (iPos%100 == 0) print ("Processed = ${iPos}");
}
print ("In fProcessData - completed ${iIters}");
}
// This loop does not work
Of course it does - you enter it exactly once, where you immediately return and therefore leave the loop and method.
// always gets here
That's because whenComplete() always gets called, on success or on error.
// it never gets here
Because you already returned out of the method.
So what can be done?
The easiest way would be to not rely on fGetUserInput(). Listen to stdin in fGetNumber and only complete the completer / cancel the subscription if the input is valid:
async.Future<int> fGetNumber(String sPrompt, int iMin, int iMax) {
print ("In fGetNumber");
async.Completer<String> oCompleter = new async.Completer();
stdout.write(sPrompt);
async.Stream<String> oStream = stdin.transform(new StringDecoder());
async.StreamSubscription oSub;
oSub = oStream.listen((String sData) {
try {
int iIters = int.parse(sData);
if (iIters < iMin || iIters > iMax) throw new Exception("Invalid");
oCompleter.complete(iIters);
oSub.cancel();
} catch(e) {
print("Invalid - number must be from ${iMin} to ${iMax}");
stdout.write(sPrompt);
}
});
return oCompleter.future;
}
Are there alternatives?
Of course. There are likely many, many ways to do this. This one for example:
async.Future<int> fGetNumber(String sPrompt, int iMin, int iMax) {
print ("In fGetNumber");
async.Completer<int> oCompleter = new async.Completer();
fGetUserInput(sPrompt, oCompleter, (String sIters) {
try {
int iIters = int.parse(sIters);
if (iIters < iMin || iIters > iMax) throw new Exception("Invalid");
return iIters;
} catch(e) {
print ("Invalid - number must be from ${iMin} to ${iMax}");
stdout.write(sPrompt);
}
return null;
});
return oCompleter.future;
}
void fGetUserInput(String sPrompt, async.Completer oCompleter, dynamic inputValidator(String sData)) {
print ("In fGetUserInput");
stdout.write(sPrompt);
async.Stream<String> oStream = stdin.transform(new StringDecoder());
async.StreamSubscription oSub;
oSub = oStream.listen((String sData) {
var d = inputValidator(sData);
if(d != null) {
oCompleter.complete(d);
oSub.cancel();
}
});
}
If you really feel there should be something addressed by the Dart team, you could write a feature request. But the Completer is designed to only be completed once. Whatever code you write, you can't just loop to complete it again and again.
Here is my code for a cellular automaton I am working on:
UPDATE:
public class Lif1ID {
private Rule rule;
private int stepCount;
public static void main (String [ ] args) {
Lif1ID simulation = new Lif1ID ( );
simulation.processArgs (args);
simulation.producePBM ( ); LINE 9
}
// Print, in Portable Bitmap format, the image corresponding to the rule and step count
// specified on the command line.
public void producePBM ( ) {
int width = (stepCount*2+1);
System.out.println("P1 " + width + " " + (stepCount+1));
String prev_string = "";
// constructs dummy first line of rule
for (int i = 0; i < width; i++){
if (i == stepCount+1){
prev_string += "1";
} else {
prev_string += "0";
}
}
// contructs and prints out all lines prescribed by the rule, including the first
for (int i = 0; i < stepCount; i++) {
String next_string = "";
for (int j = 0; j < width; j++) {
// prints next line, one character at a time
System.out.print(prev_string.charAt(j) + " ");
// specifies cases for the edges as well as for normal inputs to Rule
if (j == 0) {
next_string += rule.output(0, Character.getNumericValue(prev_string.charAt(0)), Character.getNumericValue(prev_string.charAt(1)));
} else if (j == width-1) {
next_string += rule.output(Character.getNumericValue(prev_string.charAt(width-2)), Character.getNumericValue(prev_string.charAt(width-1)), 0);
} else {
String rule_input = prev_string.substring(j-1, j+2);
int first = Character.getNumericValue(rule_input.charAt(0));
int second = Character.getNumericValue(rule_input.charAt(1));
int third = Character.getNumericValue(rule_input.charAt(2));
next_string += rule.output(first, second, third); LINE 43
}
}
// sets prev_string to next_string so that string will be the next string in line to be printed
prev_string = next_string;
System.out.println();
}
}
// Retrieve the command-line arguments, and convert them to values for the rule number
// and the timestep count.
private void processArgs (String [ ] args) {
if (args.length != 2) {
System.err.println ("Usage: java Life1D rule# rowcount");
System.exit (1);
}
try {
rule = new Rule (Integer.parseInt(args[0]));
} catch (Exception ex) {
System.err.println ("The first argument must specify a rule number.");
System.exit (1);
}
try {
stepCount = Integer.parseInt (args[1]);
} catch (Exception ex) {
System.err.println ("The second argument must specify the number of lines in the output.");
System.exit (1);
}
if (stepCount < 1) {
System.err.println ("The number of output lines must be a positive number.");
System.exit (1);
}
}
}
class Rule {
private int a, b, c;
private String rulebin;
public Rule (int ruleNum) {
rulebin = convertToBinary(ruleNum);
}
private String convertToBinary(int input) // get the binary presentation as you want
{ // if the input is 2 you'll get "00000010"
String binary = "";
for (int i = 0; i < 8; i++){
if ((1 << i & input) != 0)
binary += "1";
else
binary+= "0";
}
binary = new StringBuffer(binary).reverse().toString();
return binary;
}
// Return the output that this rule prescribes for the given input.
// a, b, and c are each either 1 or 0; 4*a+2*b+c is the input for the rule.
public char output (int a, int b, int c) {
return rulebin.charAt(7 - 4*a + 2*b + c); LINE 106
}
}
Here is the error message I get when I type in rule 30 with 3 timesteps:
java Life1D 30 3
UPDATED error message:
P1 7 4
0 0 0 0Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 151
at java.lang.String.charAt(String.java:686)
at Rule.output(Life1D.java:106)
at Life1D.producePBM(Life1D.java:43)
at Life1D.main(Life1D.java:9)
The corresponding lines are noted in the code. Why am I getting this error, and how can I fix it? I've been trying to find the error for hours, and it'll a blessing if I could be helped.
The problem is that Rule.output() expects three int parameters, but what you're calling it with on the line
next_string += rule.output(0, prev_string.charAt(0), prev_string.charAt(1));
is actually an int and then 2 chars. Now, the actual character is '0', but due to the implicit conversion the language does for you, you get the ASCII code of '0', which is 48 and that's what's passed to the function Rule.output().
Now, to fix this problem you need to use the method Character.getNumericValue() like so:
next_string += rule.output(0, Character.getNumericValue(prev_string.charAt(0)), Character.getNumericValue(prev_string.charAt(1)));
Don't forget to change the other two invocations of Rule.output()
However, note that this is not the only problem in your code, as I'm still getting String index out of range: 7, because the parameters with which the Rule.output() method is called with are now all 0, but I've answered your original question. If you need more help, let me know.