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I'm trying to call a function recursively (for sorting purposes) but getting an error. I tried to find a solution and found How to call function recursively; I changed my code accordingly, so now it looks like this:

$scope.orderCustom = function() {

    qS.quickSort($scope.mydata, 0, mydata.length-1);
};

var qS = {
    quickSort: function quickSort(data, min, max) {

        if (min < max) {
            var p = qSP.quickSortPartition(data, min, max);
            var newMax = p-1;
            var newMin = p+1;

            qS.quicksort(data, min, newMax);
            qS.quicksort(data, newMin, max);
        }
    }
};

var qSP = {
    quickSortPartition: function quickSortPartition(data, min, max) {

        var pivot = data[max].id;
        var i = min;
        for (var j = min; j <= max; j++) {
            if (data[j].id <= pivot) {
                var pom = data[j];
                data[j] = data[i];
                data[i] = pom;
                i = i+1;
            }
        }  
        var pom = data[i];
        data[i] = data[max];
        data[max] = pom;    

        return i;
    }
};

I'm getting an error "Error: qS.quicksort is not a function". Does anyone know how to solve this problem? I am still not able to leave a comment on stackoverflow, so I had to open a new question for this. Any help would be appriciated. Thanx :)

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  • Just call quickSort Commented Sep 20, 2016 at 10:16

2 Answers 2

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The simplest thing would be to get rid of the extra wrapping and just use the functions:

$scope.orderCustom = function() {

    quickSort($scope.mydata, 0, mydata.length-1);
};

function quickSort(data, min, max) {

        if (min < max) {
            var p = quickSortPartition(data, min, max);
            var newMax = p-1;
            var newMin = p+1;

            quickSort(data, min, newMax);
            quickSort(data, newMin, max);
        }
}

function quickSortPartition(data, min, max) {

        var pivot = data[max].id;
        var i = min;
        for (var j = min; j <= max; j++) {
            if (data[j].id <= pivot) {
                var pom = data[j];
                data[j] = data[i];
                data[i] = pom;
                i = i+1;
            }
        }  
        var pom = data[i];
        data[i] = data[max];
        data[max] = pom;    

        return i;
}

Note that you also have to correct the spelling of the recursive call quickSort as you had used all lower case quicksort.

I assume this is just a programming exercise as you would be better for real code to use the built-in sort() function or for angular you might prefer the orderBy filter.

For example, this does the same as you look to be trying to do:

function compare(a,b) {
  if (a.id < b.id)
    return -1;
  if (a.id > b.id)
    return 1;
  return 0;
}

$scope.mydata.sort(compare);
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6 Comments

Aaaah, what a stupid mistake. Sure, the thing was in a typo, quicksort instead of quickSort. Nice catch. Ofcourse it works now, without wrapping (as I initially wrote it). Thank you so much, it would bug me for who knows how long :)
Btw, I can't use orderBy here, that is why I am writing sort by myself (see stackoverflow.com/questions/39572744/…)
@ljerka, you should be able to just call sort with a comparison function, see the edit to my post.
Sorry if this is a stupid question, I am quite new in those stuff... But if I write $scope.mydata.sort(compare), how does compare(a, b) "know" what are my a & b? Btw, what I am trying to sort is a collection that has an id from another collection, and I would like to sort it by a name property from that other collection. So it is not so simple as to compare 2 id-s
a and b are the values the sort function wants to compare, so elements of the array being sorted. If I understand you, you actually want to compare othercollection[a.id].someattribute < othercollection[b.id].someattribute ? It makes the compare function longer but not much harder.
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You don't need to mention qS.

Just quicksort instead of qS.quicksort.

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