OpenEuphoria

Re: Your thoughts on two item id methods?

• Posted by Jason Gade <jaygade at yahoo.com> Oct 19, 2005
• 494 views

Al Getz wrote:
> 
> Hello there,
> 
> 
> Im looking at something that needs to tell the difference between two
> different classes of elements in a loop.  The two methods presented
> here both work, but they work somewhat different.  I'd like to hear
> any thoughts anyone has on these two methods, as to which one if any
> seems better and why...
> 
> METHOD #1
> 
> Atoms are of one class, while sequences are of the other class.
> Here, we know items of class 1 are atoms, while class 2 items are sequences.
> This way we can tell the difference between class 1 items and class 2 items...
> 
> itemlist={ 1,2,3,{8,9},4,{6,7} } --atoms and sequences
> for k=1 to length(itemlist) do
>   item=itemlist[k]--atom or seq
>   if atom(item) then
>     DoClass1Stuff(item)
>   else
>     DoClass2Stuff(item)
>   end if
> end for
> 
> 
> METHOD #2
> 
> Atoms will be in a sequence where the first element is zero, while
> the other class will always have a '1' as first element with the real
> data in elements 2 and above.  Thus, class 1 elements start with a zero
> and class 2 elements start with a 1...
> 
> itemlist={ {0,1},{0,2},{0,3},{1,8,9},{0,4},{1,6,7} } --all sequences
> 
> for k=1 to length(itemlist) do
>   item=itemlist[k]--always a sequence
>   if item[1] then
>     DoClass2Stuff(item)
>   else
>     DoClass1Stuff(item)
>   end if
> end for
> 
> I'm not that worried about the increase in memory space taken by
> the second method.
> In each itemlist there will be approx the same number of class 1 items
> as there are class 2 items.
> 
> Thanks for your time and thoughts...
> 
> 
> Take care,
> Al
> 
> And, good luck with your Euphoria programming!
> 
> My bumper sticker: "I brake for LED's"
> 

I would use the second method, because it is more extensible as has been pointed
out.

One thing that I noticed while thinking about strings and structures, is that
for any sequence except the empty sequence, you can actually acess two known
members: sequence[1] and sequence[$]. I was thinking to add type-data to
sequence[$] in sequences representing strings or structures. That way normal
elements can be accessed with sequence[1..$] in a more natural way.

Or embed a routine id as your marker value and for each loop iteration do 

dc1 = routine_id("DoClass1Stuff")
dc2 = routine_id("DoClass2Stuff")
itemlist={ {dc1,1},{dc1,2},{dc1,3},{dc2,8,9},{dc1,4},{dc2,6,7} } --all sequences

for k=1 to length(itemlist) do
  item=itemlist[k]--always a sequence
  call_proc(item[1], {item})  
end for

j.