Re: Delete the first entry of an array.

[Mike Kerner]

don't make me go all LISP on you...or APL

On Sun, Mar 27, 2016 at 7:03 PM, Dr. Hawkins  wrote:

> On Sat, Mar 26, 2016 at 4:40 PM, Alex Tweedly  wrote:
>
> > e, and hence be able to do completely dense arrays, just like Fortran
> etc.
> > (he said, making about 50 wild assumptions about a language he can't
> find a
> > spec for :-)
>
>
> Just to throw gas on the flames (petrol for you cross-atlantans) . . .
>
> Fortran can have sparse arrays, far larger than memory or disk storage . .
> .
>
>
> --
> Dr. Richard E. Hawkins, Esq.
> (702) 508-8462
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-- 
On the first day, God created the heavens and the Earth
On the second day, God created the oceans.
On the third day, God put the animals on hold for a few hours,
   and did a little diving.
And God said, "This is good."
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Re: (way OT, WAS: )Re: Delete the first entry of an array.

[J. Landman Gay]

On 3/27/2016 6:59 PM, Dr. Hawkins wrote:

I've been out-crankied!


LOL. But actually I think the final score is three out of four, so you 
are still in the running. :)


--
Jacqueline Landman Gay | jac...@hyperactivesw.com
HyperActive Software   | http://www.hyperactivesw.com

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Re: (way OT, WAS: )Re: Delete the first entry of an array.

[Dr. Hawkins]

On Sun, Mar 27, 2016 at 4:36 PM, Alex Tweedly  wrote:

> Hmmm ... not real Fortran. (that should be said in a deep, impressive
> voice)
> Real Fortran died when Fortran 77 took over :-(
>

I've been out-crankied!

>
> And, AFAIK, only those modern variants from (I think) Fortran90 onwards
> have sparse arrays.
>

Yes, I designed the algorithm for my dissertation in Fortran 90, longing
for some of the F95 features that weren't available yet.

Sparse arrays would have been useful, except for the detail that the
elements that I *was* generating in my search dwarfed the size of physical
memory . . .



-- 
Dr. Richard E. Hawkins, Esq.
(702) 508-8462
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Re: Delete the first entry of an array.

[Dr. Hawkins]

On Sat, Mar 26, 2016 at 4:40 PM, Alex Tweedly  wrote:

> e, and hence be able to do completely dense arrays, just like Fortran etc.
> (he said, making about 50 wild assumptions about a language he can't find a
> spec for :-)


Just to throw gas on the flames (petrol for you cross-atlantans) . . .

Fortran can have sparse arrays, far larger than memory or disk storage . . .


-- 
Dr. Richard E. Hawkins, Esq.
(702) 508-8462
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Re: Delete the first entry of an array.

[Alex Tweedly]

On 27/03/2016 20:47, Ali Lloyd wrote:

True - but sadly there's no effective way to filter those 523 entries to
see only the ones that are relevant to a List type.

One way to do this is to click the 'lists' filter in the tags section.

Thanks.
I had tried typing 'list' into the search box, which 
over-enthusiastically reduced the entries to only 7 :-)


The tag works much better 

Thanks
-- Alex.

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Re: Delete the first entry of an array.

[Ali Lloyd]

> True - but sadly there's no effective way to filter those 523 entries to
> see only the ones that are relevant to a List type.

One way to do this is to click the 'lists' filter in the tags section.

On Sun, Mar 27, 2016 at 5:33 PM Alex Tweedly  wrote:

>
>
> On 27/03/2016 10:42, Peter TB Brett wrote:
> > On 26/03/2016 23:40, Alex Tweedly wrote:
> >> I haven't found (can't find) a spec for LCB, so I'm not sure exactly
> >> what "proper lists" are - but I think maybe not quite what I meant.
> >
> > There's a spec in the "Guides" tab of the LC8 dictionary -- look for
> > "LiveCode Builder Language Reference".
> I see that, but the ONLY mention it makes of lists are:
>   - it is one of the Types
>   - it holds a "sequence of values"
>   - what a ListExpression is.
>
> > There's also a whole LCB dictionary section in the "Dictionary" tab
> > that describes all the syntax relating to working with Lists.
> True - but sadly there's no effective way to filter those 523 entries to
> see only the ones that are relevant to a List type.
> >
> >> I was thinking of "proper arrays" :-) i.e. real, old-fashioned indexed
> >> arrays - see Algol, Fortran, etc.
> >>
> >> So we would have
> >> read access in constant time
> >> write access in constant time
> >> insertion complexity - there is no such thing as insertion :-)
> >
> > Yes.  We're talking about the same thing.  The LCB "List" datatype is
> > this datastructure.
> >
> I suspect we're not quite talking about the same thing - I think 'proper
> lists' are something more powerful than I was picturing, but can do
> everything I am looking for - and a whole lot more. If I simply ignore
> all that "more", then they do what I am hoping for.
>
> Many thanks for you patience explaining this.
> I'll go start playing with LCB and try to ask harder questions :-)
>
> Thanks
> -- Alex.
>
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Re: Delete the first entry of an array.

[Alex Tweedly]

On 27/03/2016 10:42, Peter TB Brett wrote:

On 26/03/2016 23:40, Alex Tweedly wrote:

I haven't found (can't find) a spec for LCB, so I'm not sure exactly
what "proper lists" are - but I think maybe not quite what I meant.


There's a spec in the "Guides" tab of the LC8 dictionary -- look for 
"LiveCode Builder Language Reference".

I see that, but the ONLY mention it makes of lists are:
 - it is one of the Types
 - it holds a "sequence of values"
 - what a ListExpression is.

There's also a whole LCB dictionary section in the "Dictionary" tab 
that describes all the syntax relating to working with Lists.
True - but sadly there's no effective way to filter those 523 entries to 
see only the ones that are relevant to a List type.



I was thinking of "proper arrays" :-) i.e. real, old-fashioned indexed
arrays - see Algol, Fortran, etc.

So we would have
read access in constant time
write access in constant time
insertion complexity - there is no such thing as insertion :-)


Yes.  We're talking about the same thing.  The LCB "List" datatype is 
this datastructure.


I suspect we're not quite talking about the same thing - I think 'proper 
lists' are something more powerful than I was picturing, but can do 
everything I am looking for - and a whole lot more. If I simply ignore 
all that "more", then they do what I am hoping for.


Many thanks for you patience explaining this.
I'll go start playing with LCB and try to ask harder questions :-)

Thanks
-- Alex.

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Re: Delete the first entry of an array.

[Peter TB Brett]

On 26/03/2016 23:40, Alex Tweedly wrote:

I haven't found (can't find) a spec for LCB, so I'm not sure exactly
what "proper lists" are - but I think maybe not quite what I meant.


There's a spec in the "Guides" tab of the LC8 dictionary -- look for 
"LiveCode Builder Language Reference".  There's also a whole LCB 
dictionary section in the "Dictionary" tab that describes all the syntax 
relating to working with Lists.



I was thinking of "proper arrays" :-)  i.e. real, old-fashioned indexed
arrays - see Algol, Fortran, etc.

So we would have
read access in constant time
write access in constant time
insertion complexity - there is no such thing as insertion :-)


Yes.  We're talking about the same thing.  The LCB "List" datatype is 
this datastructure.


Peter

--
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LiveCode Open Source Team

LiveCode 2016 Conference https://livecode.com/edinburgh-2016/

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Re: Delete the first entry of an array.

[Alex Tweedly]

On 26/03/2016 07:35, Peter TB Brett wrote:

On 25/03/2016 23:00, Alex Tweedly wrote:


How about a Feature Exchange for adding arrays ?   (i.e. not
dictionaries, but actual arrays with numeric indices and linear access
times)


In LiveCode, we currently call these "proper lists".

LiveCode arrays currently have O(log N) read and insertion complexity 
in the general case (which is better than linear).


If we were to add proper lists, we would probably use an 
implementation with O(1) read and O(N) insertion complexity in the 
general case.



Yes, sorry, I said it badly, leading to some confusion.
I meant "linear access time" for accessing every element of the array in 
turn - i.e. (roughly) equivalent to "constant access time" for an 
individual access.
If you need proper lists, LiveCode Builder already provides them with 
the "List" type.


I haven't found (can't find) a spec for LCB, so I'm not sure exactly 
what "proper lists" are - but I think maybe not quite what I meant.


I was thinking of "proper arrays" :-)  i.e. real, old-fashioned indexed 
arrays - see Algol, Fortran, etc.


So we would have
read access in constant time
write access in constant time
insertion complexity - there is no such thing as insertion :-)

OK, given that we would never want to require array declarations to 
define bounds, there might be some extra cost on extending the bounds, 
but that would be occasional, so we would in general have constant 
access time (for either read or write).


And, of course, if it were done in LCB it would be even more 
advantageous because we would pre-define the data type, and hence be 
able to do completely dense arrays, just like Fortran etc. (he said, 
making about 50 wild assumptions about a language he can't find a spec 
for :-)


Regards
-- Alex.

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Re: Delete the first entry of an array.

[Richard Gaskin]

Peter TB Brett wrote:

On 26/03/2016 14:18, Richard Gaskin wrote:

Is there an estimate for when indexed arrays ("proper lists") may become
available in LiveCode Script?


Not currently on the roadmap.


Given how frequently it's been requested for many years I was surprised 
I couldn't find an enhancement request for it in the RQCC, so I added 
one this morning:


http://quality.livecode.com/show_bug.cgi?id=17236

--
 Richard Gaskin
 Fourth World Systems
 Software Design and Development for the Desktop, Mobile, and the Web
 
 ambassa...@fourthworld.comhttp://www.FourthWorld.com

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Re: Delete the first entry of an array.

[Peter TB Brett]

On 26/03/2016 14:18, Richard Gaskin wrote:

Is there an estimate for when indexed arrays ("proper lists") may become
available in LiveCode Script?


Not currently on the roadmap.

  Peter

--
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LiveCode Open Source Team

LiveCode 2016 Conference https://livecode.com/edinburgh-2016/

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Re: Delete the first entry of an array.

[Richard Gaskin]

Peter TB Brett wrote:
> On 25/03/2016 23:00, Alex Tweedly wrote:
>
>> How about a Feature Exchange for adding arrays ?   (i.e. not
>> dictionaries, but actual arrays with numeric indices and linear
>> access times)
>
> In LiveCode, we currently call these "proper lists".
>
> LiveCode arrays currently have O(log N) read and insertion complexity
> in the general case (which is better than linear).
>
> If we were to add proper lists, we would probably use an
> implementation with O(1) read and O(N) insertion complexity in the
> general case.
>
> If you need proper lists, LiveCode Builder already provides them with
> the "List" type.

Is there an estimate for when indexed arrays ("proper lists") may become 
available in LiveCode Script?


--
 Richard Gaskin
 Fourth World Systems
 Software Design and Development for the Desktop, Mobile, and the Web
 
 ambassa...@fourthworld.comhttp://www.FourthWorld.com


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Re: Delete the first entry of an array.

[Peter TB Brett]

On 25/03/2016 23:00, Alex Tweedly wrote:


How about a Feature Exchange for adding arrays ?   (i.e. not
dictionaries, but actual arrays with numeric indices and linear access
times)


In LiveCode, we currently call these "proper lists".

LiveCode arrays currently have O(log N) read and insertion complexity in 
the general case (which is better than linear).


If we were to add proper lists, we would probably use an implementation 
with O(1) read and O(N) insertion complexity in the general case.


If you need proper lists, LiveCode Builder already provides them with 
the "List" type.


   Peter

--
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LiveCode Open Source Team

LiveCode 2016 Conference https://livecode.com/edinburgh-2016/

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Re: Delete the first entry of an array.

[Richard Gaskin]

Alex Tweedly wrote:
> How about a Feature Exchange for adding arrays ?   (i.e. not
> dictionaries, but actual arrays with numeric indices and linear
> access times)

lulz.  Cute, but of course associative arrays are indeed a type of array.

But yes, it would be nice to also support indexed arrays.

I have a vague recollection of Mark Waddingham noting somewhere back in 
the Engine Contributors section of the forums or a bug report that 
wouldn't be hard to do.  May be my aging memory, though


--
 Richard Gaskin
 Fourth World Systems
 Software Design and Development for the Desktop, Mobile, and the Web
 
 ambassa...@fourthworld.comhttp://www.FourthWorld.com


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Re: Delete the first entry of an array.

[Alex Tweedly]

On 25/03/2016 08:03, Peter TB Brett wrote:

Hi Peter,

LiveCode arrays are actually dictionaries (more like JavaScript 
objects than JavaScript arrays).  There aren't currently any push/pop 
syntax for LiveCode arrays.


...
I hope that's helpful.

Would anyone be interested in a Feature Exchange for adding some new 
array operators (such as push and pop) to the language?


 Peter

How about a Feature Exchange for adding arrays ?   (i.e. not 
dictionaries, but actual arrays with numeric indices and linear access 
times)


-- Alex.

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Re: Delete the first entry of an array.

[Mike Bonner]

Leave things as they are, delete the first element, and keep track of an
offset value that you use to grab array elements.  If your array starts at
1, and you haven't deleted any elements from the front, the offset is 0.
If you delete 2 items, from the front, the offset is 2.  If you want to
access the 4th element, it would be arrayval[itemnum+offset]  You could
generate the offset by grabbing the keylist, sorting it, and grabbing the
first key - 1 (or use min() -1) but it would probably be far more efficient
to just keep track as you go.  You could keep the offset value in the array
too.

Of course, this doesn't help if you are removing elements from the middle
of the numerically indexed array too.  (in which case it would just make
sense to keep a sorted list of keys and preform duplicate operations on the
list. Then you can use line 3 of the keylist  as your array key for the
proper item.

Having said all that, I'm all for a feature exchange to make this sort of
thing easier.  Yes please! (I don't have much discretionary spending moola,
but this one would garner some of it)

On Fri, Mar 25, 2016 at 4:25 AM, Peter W A Wood 
wrote:

> Thanks Kay
>
> > On 25 Mar 2016, at 17:22, Kay C Lan  wrote:
> >
> > On Fri, Mar 25, 2016 at 3:33 PM, Peter W A Wood 
> wrote:
> >
> >>  delete pList[“numbers”] 1 ## Is
> this the correct syntax?
> >
> > No. Shouldn't it be:
> >
> > delete variable pList["number"][1]
> >
> > At least that works for me, although in your case I think, if I
> > understand it correctly, I'd tackle the problem by: (suedo-code)
> >
> > repeat with x = 2 to the number of keys in firstArray
> >  put firstArray[x] into secondArray[x - 1]
> > end repeat
> > put secondArray into firstArray
>
>
> I do something like this at the moment. I was trying to see if there was
> an easier/quicker way.
>
> Kind regards
>
> Peter
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Feature Exchange for Array extensions (Was Re: Delete the first entry of an array.)

[Paul Dupuis]

On 3/25/2016 4:03 AM, Peter TB Brett wrote:
> Would anyone be interested in a Feature Exchange for adding some new
> array operators (such as push and pop) to the language?
>
>  Peter

I'm not very interested in a push and pop functions, but what I have
been wanting for quite some time is really good row and column
operations on 2 dimensional numerically index arrays.
LC Bugzilla entries 670, 4623, 7243, and 9950 are a few enhancements
requests related to this need

I really want to have chunk expressions for a 2D array, such as "put row
3 of somearray into tVar" OR, the really handy one, "put column 5 of
myArray into AColumn" and even things like "get word 2 of first row of
last column of anotherarray"
Similar with "delete row 7" or "put empty into column 6" or " put 0 into
column 6" (replace all cells in column 6 with zero). Also an associated
modifications to "split" and "combine" to turn delimited (typically tab
and cr) data into a 2D numerically indexed array and 2D numerically
index arrays into delimited data

Obviously, these functions can be coded (and have been) as LC script
handlers, but I find myself working with table data frequently enough
that I really would like them to be part of the engine.


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Re: Delete the first entry of an array.

[Peter W A Wood]

Thanks Kay

> On 25 Mar 2016, at 17:22, Kay C Lan  wrote:
> 
> On Fri, Mar 25, 2016 at 3:33 PM, Peter W A Wood  wrote:
> 
>>  delete pList[“numbers”] 1 ## Is this 
>> the correct syntax?
> 
> No. Shouldn't it be:
> 
> delete variable pList["number"][1]
> 
> At least that works for me, although in your case I think, if I
> understand it correctly, I'd tackle the problem by: (suedo-code)
> 
> repeat with x = 2 to the number of keys in firstArray
>  put firstArray[x] into secondArray[x - 1]
> end repeat
> put secondArray into firstArray


I do something like this at the moment. I was trying to see if there was an 
easier/quicker way.

Kind regards

Peter
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Re: Delete the first entry of an array.

[Kay C Lan]

On Fri, Mar 25, 2016 at 3:33 PM, Peter W A Wood  wrote:

>   delete pList[“numbers”] 1 ## Is this 
> the correct syntax?

No. Shouldn't it be:

delete variable pList["number"][1]

At least that works for me, although in your case I think, if I
understand it correctly, I'd tackle the problem by: (suedo-code)

repeat with x = 2 to the number of keys in firstArray
  put firstArray[x] into secondArray[x - 1]
end repeat
put secondArray into firstArray

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Re: Delete the first entry of an array.

[Peter W A Wood]

Peter

Thanks for the suggestions.

> On 25 Mar 2016, at 16:03, Peter TB Brett  wrote:
> 
> On 2016-03-25 08:33, Peter W A Wood wrote:
>> I have an array which contains a second array. (myArray[“numbers”][]).
>> ...
>> automatically change the index of the remaining entries?
> 
> Hi Peter,
> 
> LiveCode arrays are actually dictionaries (more like JavaScript objects than 
> JavaScript arrays).  There aren't currently any push/pop syntax for LiveCode 
> arrays.

Thanks for the confirmation as I wasn’t sure that was the case for all arrays 
due to the existence of the extents function.

> I would recommend two things:
> 
> 1) Arrange your algorithm so that you extract things one-by-one from the 
> _end_ of the numbered array, rather than the start.  This is more efficient!  

It is not possible in this case as the order of the elements is significant. I 
use a different function to remove the last element of the array.

> 
> 2) Alternatively, you can shift everything along, which will be slow:
> 
>   function PopStart @xArray
>  local tLength, tItem, tKey
> 
>  put the number of elements in xArray into tLength
>  if tLength is 0 then return empty
> 
>  put xArray[1] into tItem
> 
>  repeat with tKey = 2 to tLength
> put xArray[tKey] into xArray[tKey - 1]
>  end repeat
>  delete xArray[tLength]
> 
>  return tItem
>   end PopStart

This is what I am currently having to do but am not too worried yet as I 
believe in the “Getting it working, getting it working correctly, getting 
working quickly approach”.

> I hope that's helpful.

Thanks for the suggestions.

Kind regards

Peter



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Re: Delete the first entry of an array.

[Peter TB Brett]

On 2016-03-25 08:33, Peter W A Wood wrote:

I have an array which contains a second array. (myArray[“numbers”][]).
The numbers array is a traditional array with elements 1..n. I want to
remove the first element of the numbers array and shuffle all the
others up. Is there a simple way of doing this in LiveCode (equivalent
to the shift() function in JavaScript)?

I looked in the dictionary and found delete  but couldn't
get it to work, perhaps because I am trying to do this in a function
that takes the array as an argument.

The essence of the function is:

function shift @pList
  local tItem
  put pList[“numbers”][1] into tItem
  delete pList[“numbers”] 1 ## Is this the 
correct syntax?
  return tItem
end shift

If I can get delete to remove the first element of the array, will it
automatically change the index of the remaining entries?


Hi Peter,

LiveCode arrays are actually dictionaries (more like JavaScript objects 
than JavaScript arrays).  There aren't currently any push/pop syntax for 
LiveCode arrays.


I would recommend two things:

1) Arrange your algorithm so that you extract things one-by-one from the 
_end_ of the numbered array, rather than the start.  This is more 
efficient!  Then you would do something like:


   function PopEnd @xArray
  local tLength, tItem

  put the number of elements in xArray into tLength
  if tLength is 0 then return empty

  put xArray[tLength] into tItem

  delete xArray[tLength]

  return tItem
   end PopEnd

2) Alternatively, you can shift everything along, which will be slow:

   function PopStart @xArray
  local tLength, tItem, tKey

  put the number of elements in xArray into tLength
  if tLength is 0 then return empty

  put xArray[1] into tItem

  repeat with tKey = 2 to tLength
 put xArray[tKey] into xArray[tKey - 1]
  end repeat
  delete xArray[tLength]

  return tItem
   end PopStart

3) Another option, if you don't care about what order you get your 
values in, is to remove an item from anywhere, cheaply, by moving the 
last item in the list on top of the one you've removed:


   function RemoveAt @xArray, pIndex
  local tLength, tItem

  if pIndex is not among the keys of xArray then return empty
  put the number of elements in xArray into tLength

  put xArray[pIndex] into tItem
  put xArray[tLength] into xArray[pIndex]
  delete xArray[tLength]

  return tItem
   end RemoveAt


I hope that's helpful.

Would anyone be interested in a Feature Exchange for adding some new 
array operators (such as push and pop) to the language?


 Peter

--
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LiveCode Open Source Team

LiveCode 2016 Conference https://livecode.com/edinburgh-2016/

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Delete the first entry of an array.

[Peter W A Wood]

I have an array which contains a second array. (myArray[“numbers”][]). The 
numbers array is a traditional array with elements 1..n. I want to remove the 
first element of the numbers array and shuffle all the others up. Is there a 
simple way of doing this in LiveCode (equivalent to the shift() function in 
JavaScript)?

I looked in the dictionary and found delete  but couldn't get it to 
work, perhaps because I am trying to do this in a function that takes the array 
as an argument.

The essence of the function is:

function shift @pList
  local tItem
  put pList[“numbers”][1] into tItem
  delete pList[“numbers”] 1 ## Is this the 
correct syntax?
  return tItem
end shift

If I can get delete to remove the first element of the array, will it 
automatically change the index of the remaining entries?

Thanks in advance.

Peter
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