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Remove leading zeros in index of array

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  Remove leading zeros in index of array jonas.thornvall@gmail.com - 2015-03-23 04:57 -0700
    Re: Remove leading zeros in index of array jonas.thornvall@gmail.com - 2015-03-23 10:03 -0700
      Re: Remove leading zeros in index of array Scott Sauyet <scott.sauyet@gmail.com> - 2015-03-23 10:32 -0700
      Re: Remove leading zeros in index of array Tim Streater <timstreater@greenbee.net> - 2015-03-23 18:36 +0000
      Re: Remove leading zeros in index of array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-03-23 20:42 +0100
        Re: Remove leading zeros in index of array jonas.thornvall@gmail.com - 2015-03-23 12:58 -0700
          Re: Remove leading zeros in index of array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-03-23 21:12 +0100
            Re: Remove leading zeros in index of array jonas.thornvall@gmail.com - 2015-03-23 13:16 -0700
              Re: Remove leading zeros in index of array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-03-23 21:36 +0100
                Re: Remove leading zeros in index of array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-03-23 21:49 +0100
                  Re: Remove leading zeros in index of array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-03-23 21:58 +0100
    Re: Remove leading zeros in index of array Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2015-03-24 15:41 +0100
      Re: Remove leading zeros in index of array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-24 20:21 +0100
        Re: Remove leading zeros in index of array Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2015-03-24 20:45 +0100
          Re: Remove leading zeros in index of array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-24 20:47 +0100
      Re: Remove leading zeros in index of array Scott Sauyet <scott.sauyet@gmail.com> - 2015-03-24 13:37 -0700
        Re: Remove leading zeros in index of array Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2015-03-25 00:01 +0100

#27109 — Remove leading zeros in index of array

I store integers in the indexes of an array, is there a prefared or easy way to remove all leading indexes  containing zeros?

To use splice i have to loop thru the array?

bin=[0,0,0,1,0,1,0,1]

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#27110

Den måndag 23 mars 2015 kl. 12:58:08 UTC+1 skrev jonas.t...@gmail.com:
> I store integers in the indexes of an array, is there a prefared or easy way to remove all leading indexes  containing zeros?
> 
> To use splice i have to loop thru the array?
> 
> bin=[0,0,0,1,0,1,0,1]

This is what i've come up with.

while (result[length]==0)  {result.splice(length, 1);length+=-1;}

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#27111

jonas.thornvall@gmail.com wrote:
> jonas.thornvall@gmail.com wrote:
>> I store integers in the indexes of an array, is there a prefared 
>> or easy way to remove all leading indexes  containing zeros?
>> [ ... ] 
> This is what i've come up with.
> 
> while (result[length]==0)  {result.splice(length, 1);length+=-1;}

One possibility:

    var removeLeadingZeros = function(list) {
      var firstNonZero = 0;
      list.every(function(item, index) {
        if (item !== 0) {
          firstNonZero = index;
          return false;
        }
        return true;
      });
      return list.slice(firstNonZero);
    };

This depends on `Array.prototype.every` which is not available in JScript
before Chakra (i.e. before IE9), and would have to be polyfilled if you
wanted to use it in that environment.

While it's not a beautiful solution, it certainly seems better than
continually `splice`ing out values.  Note that this does *not* modify your
original list but returns a copy of it.  To my mind this is an advantage;
but if you prefer, you could always replace that last line with a single 
`splice` call.

  -- Scott

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#27112

In article <27052983-4f87-4ee8-9778-8337a84e359f@googlegroups.com>,
<jonas.thornvall@gmail.com> wrote:

>Den måndag 23 mars 2015 kl. 12:58:08 UTC+1 skrev jonas.t...@gmail.com:
>> I store integers in the indexes of an array, is there a prefared or easy way
>> to remove all leading indexes  containing zeros?
>> 
>> To use splice i have to loop thru the array?
>> 
>> bin=[0,0,0,1,0,1,0,1]
>
>This is what i've come up with.
>
>while (result[length]==0)  {result.splice(length, 1);length+=-1;}

Or possibly:

   length -= 1;

-- 
"People don't buy Microsoft for quality, they buy it for compatibility
with what Bob in accounting bought last year. Trace it back - they buy
Microsoft because the IBM Selectric didn't suck much" - P Seebach, afc

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#27113

jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:

> Den måndag 23 mars 2015 kl. 12:58:08 UTC+1 skrev jonas.t...@gmail.com:
>> I store integers in the indexes of an array, is there a prefared or easy 
> way to remove all leading indexes  containing zeros?
>> 
>> To use splice i have to loop thru the array?
>> 
>> bin=[0,0,0,1,0,1,0,1]
> 
> This is what i've come up with.
> 
> while (result[length]==0)  {result.splice(length, 1);length+=-1;}

var a = [0,0,0,3,0,7,0,1];

while (a[0]==0)
	a.splice(0, 1);

alert(a);

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#27114

Den måndag 23 mars 2015 kl. 20:42:54 UTC+1 skrev Evertjan.:
> jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:
> 
> > Den måndag 23 mars 2015 kl. 12:58:08 UTC+1 skrev jonas.t...@gmail.com:
> >> I store integers in the indexes of an array, is there a prefared or easy 
> > way to remove all leading indexes  containing zeros?
> >> 
> >> To use splice i have to loop thru the array?
> >> 
> >> bin=[0,0,0,1,0,1,0,1]
> > 
> > This is what i've come up with.
> > 
> > while (result[length]==0)  {result.splice(length, 1);length+=-1;}
> 
> var a = [0,0,0,3,0,7,0,1];
> 
> while (a[0]==0)
> 	a.splice(0, 1);
> 
> alert(a);
> 
> -- 
> Evertjan.
> The Netherlands.
> (Please change the x'es to dots in my emailaddress)

Sorry Evertjan i probably wrote in the values wrong way out of head, the zeros will range from highest index.

But while 
 while (a[length]==0) {a.splice(length, 1);length--;}
 alert(a);

while (result[length]==0)  {result.splice(length, 1);length+=-1;} 
Basicly same.

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#27115

jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:

> Sorry Evertjan i probably wrote in the values wrong way out of head, the
> zeros will range from highest index. 
> 
> But while 
>  while (a[length]==0) {a.splice(length, 1);length--;}
>  alert(a);
> 
> while (result[length]==0)  {result.splice(length, 1);length+=-1;} 
> Basicly same.

Not the same, you sh/could use pop() here:

=============================
var a = [3,0,7,0,1,0,0,0]

while (a[a.length-1]==0) a.pop();

alert(a);
=============================

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#27116

Den måndag 23 mars 2015 kl. 21:12:28 UTC+1 skrev Evertjan.:
> jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:
> 
> > Sorry Evertjan i probably wrote in the values wrong way out of head, the
> > zeros will range from highest index. 
> > 
> > But while 
> >  while (a[length]==0) {a.splice(length, 1);length--;}
> >  alert(a);
> > 
> > while (result[length]==0)  {result.splice(length, 1);length+=-1;} 
> > Basicly same.
> 
> Not the same, you sh/could use pop() here:
> 
> =============================
> var a = [3,0,7,0,1,0,0,0]
> 
> while (a[a.length-1]==0) a.pop();
> 
> alert(a);
> =============================
> 
> -- 
> Evertjan.
> The Netherlands.
> (Please change the x'es to dots in my emailaddress)

Thank you, i will try.

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#27117

jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:

>> ========================
>> var a = [3,0,7,0,1,0,0,0]
>> 
>> while (a[a.length-1]==0) a.pop();
>> 
>> alert(a);
>> ========================
>> 
> Thank you, i will try.

Since pop() returns what is popped,
you could try this less efficient,
but perhaps also enjoyable way:

====================
var a = [3,0,7,0,1,0,0,0];
var b = a.slice(); // copy array a to b

while (b.pop() == 0) {a.pop()};

alert(a);
====================

and if you want to see what is happening, 
insert an alert():

while (b.pop() == 0) {alert(a.pop())};


-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#27118

"Evertjan." <exxjxw.hannivoort@inter.nl.net> wrote on 23 mrt 2015 in 
comp.lang.javascript:

> jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:
> 
>>> ========================
>>> var a = [3,0,7,0,1,0,0,0]
>>> 
>>> while (a[a.length-1]==0) a.pop();
>>> 
>>> alert(a);
>>> ========================
>>> 
>> Thank you, i will try.
> 
> Since pop() returns what is popped,
> you could try this less efficient,
> but perhaps also enjoyable way:
> 
> ====================
> var a = [3,0,7,0,1,0,0,0];
> var b = a.slice(); // copy array a to b
> 
> while (b.pop() == 0) {a.pop()};
> 
> alert(a);
> ====================

Or push the popped nonzero element back:

=================
var a = [3,0,7,0,1,0,0,0], temp;

while ( (temp = a.pop()) == 0) {};

a.push(temp);

alert(a);
=================

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#27119

"Evertjan." <exxjxw.hannivoort@inter.nl.net> wrote on 23 mrt 2015 in 
comp.lang.javascript:

> "Evertjan." <exxjxw.hannivoort@inter.nl.net> wrote on 23 mrt 2015 in 
> comp.lang.javascript:
> 
>> jonas.thornvall@gmail.com wrote on 23 mrt 2015 in comp.lang.javascript:
>> 
>>>> ========================
>>>> var a = [3,0,7,0,1,0,0,0]
>>>> 
>>>> while (a[a.length-1]==0) a.pop();
>>>> 
>>>> alert(a);
>>>> ========================
>>>> 
>>> Thank you, i will try.
>> 
>> Since pop() returns what is popped,
>> you could try this less efficient,
>> but perhaps also enjoyable way:
>> 
>> ====================
>> var a = [3,0,7,0,1,0,0,0];
>> var b = a.slice(); // copy array a to b
>> 
>> while (b.pop() == 0) {a.pop()};
>> 
>> alert(a);
>> ====================
> 
> Or push the popped nonzero element back:
> 
> =================
> var a = [3,0,7,0,1,0,0,0], temp;
> 
> while ( (temp = a.pop()) == 0) {};
> 
> a.push(temp);
> 
> alert(a);
> =================

Or you could use regex, 
if the values are single digits:

===============
var a = [1,0,4,0,1,0,0,0];

a = a.join('').replace(/0*$/,'').split('');

alert(a);
===============


-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#27124

On 2015-03-23 12:57, jonas.thornvall@gmail.com wrote:
> I store integers in the indexes of an array, is there a prefared or
> easy way to remove all leading indexes  containing zeros?
>
> To use splice i have to loop thru the array?
>
> bin=[0,0,0,1,0,1,0,1]

Maybe you can use filter:

bin = bin.filter(function(element){
     if (element) {
         return element;
     }
     return false;
});

-- 
Cezary Tomczyk
http://www.ctomczyk.pl/

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#27125

Cezary Tomczyk wrote:

> bin = bin.filter(function(element){
>      if (element) {
>          return element;
>      }
>      return false;
> });

  bin = bin.filter(function (e) { return e; });

<http://ecma-international.org/ecma-262/5.1/#sec-15.4.4.20>,
step 9.c.iii.

<http://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.prototype.filter>,
step 11.d.iii.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#27126

On 2015-03-24 20:21, Thomas 'PointedEars' Lahn wrote:
> Cezary Tomczyk wrote:
>
>> bin = bin.filter(function(element){
>>       if (element) {
>>           return element;
>>       }
>>       return false;
>> });
>
>    bin = bin.filter(function (e) { return e; });

Your code is shorter then mine. However, I think it's just less readable 
in my opinion.

> <http://ecma-international.org/ecma-262/5.1/#sec-15.4.4.20>,
> step 9.c.iii.
>
> <http://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.prototype.filter>,
> step 11.d.iii.

Thanks for the links.

-- 
Cezary Tomczyk
http://www.ctomczyk.pl/

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#27127

Cezary Tomczyk wrote:

> On 2015-03-24 20:21, Thomas 'PointedEars' Lahn wrote:
>> Cezary Tomczyk wrote:
>>> bin = bin.filter(function(element){
>>>       if (element) {
>>>           return element;
>>>       }
>>>       return false;
>>> });
>>
>>    bin = bin.filter(function (e) { return e; });
> 
> Your code is shorter then mine. However, I think it's just less readable
> in my opinion.

Wait till ES 6 (or use Node.js which already supports this):

  bin = bin.filter(e => e);

;-)

<https://github.com/joyent/node/wiki/ES6-%28a.k.a.-Harmony%29-Features-Implemented-in-V8-and-Available-in-Node>

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#27128

Cezary Tomczyk wrote:
> jonas.thornvall@gmail.com wrote:
>> I store integers in the indexes of an array, is there a prefared or
>> easy way to remove all leading indexes  containing zeros?
>>
>> To use splice i have to loop thru the array?
>>
>> bin=[0,0,0,1,0,1,0,1]
> 
> Maybe you can use filter:
> 
> bin = bin.filter(function(element){
>      if (element) {
>          return element;
>      }
>      return false;
> });

This would result in `[1, 1, 1]` for the above input, when the OP asked
for the removal of only the _leading_ zeros: `[`1, 0, 1, 0, 1]`.  (This
was amended in a later post to ask for the removal of trailing zeros,
but in either case, this technique would fail.

For leading zeros, the following should do it, returning a new array:


    var i = 0; while (arr[i] == 0) {i+=1;} arr.slice(i);

And if you really want to modify the existing array, you could do this:

    var i = 0; while (arr[i] == 0) {i+=1;} arr.splice(0, i);
    arr;


And similarly for trailing zeros:

    var i = arr.length - 1; while (arr[i] == 0) {i-=1;} arr.slice(0, i + 1);

or to modify in place:

    var i = arr.length - 1; while (arr[i] == 0) {i-=1;} 
    arr.splice(i + 1, arr.length - i - 1); 
    arr;


  -- Scott

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#27129

On 2015-03-24 21:37, Scott Sauyet wrote:
> Cezary Tomczyk wrote:
>> jonas.thornvall@gmail.com wrote:
>>> I store integers in the indexes of an array, is there a prefared or
>>> easy way to remove all leading indexes  containing zeros?
>>>
>>> To use splice i have to loop thru the array?
>>>
>>> bin=[0,0,0,1,0,1,0,1]
>>
>> Maybe you can use filter:
>>
>> bin = bin.filter(function(element){
>>       if (element) {
>>           return element;
>>       }
>>       return false;
>> });
>
> This would result in `[1, 1, 1]` for the above input, when the OP asked
> for the removal of only the _leading_ zeros: `[`1, 0, 1, 0, 1]`.  (This
> was amended in a later post to ask for the removal of trailing zeros,
> but in either case, this technique would fail.

You're right. I've overlooked requirement for removal of only the 
leading zeros.

> For leading zeros, the following should do it, returning a new array:

I was just experimenting (for fun) and created one line solution:

bin.toString().replace(/^(0,)+?(?=[1-9])/, '').split();

It has limits, of course, but can be extended in many ways :-)

-- 
Cezary Tomczyk
http://www.ctomczyk.pl/

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