OpenEuphoria

Re: 0-based Indexing

• Posted by Juergen Luethje <j.lue at gmx.de> Jul 17, 2003
• 506 views

Hi Igor, you wrote:

> If you have many basic arrays with 0-indexing and want
> to translate them into EU, yes, this is a real pain and
> a rich source of the subtle bugs, especially when
> indexes are calculated.
>
> I have dropped some my translations from basic into EU
> just because of too many confusions in indexes,
> especially if some of the 0-elements
> are or are not empty.
>
> Maybe, someone has a powerful tip,
> other than just a good attention?

Instead of creating, writing, and reading the arrays/sequences directly,
you can access them via functions. Of course, you have the full power
and flexibility of Euphoria.  Here is just an example:

-----------------------------[ begin code ]-----------------------------
constant LBOUND = 1, UBOUND = 2

global function array_dim (sequence bounds, object initVal)
   -- create an one-dimensional 'array' with arbitrary bounds
   -- (even negative indexes are allowed)
   integer lBound, uBound
   lBound = bounds[LBOUND]
   uBound = bounds[UBOUND]
   if lBound > uBound then
      return -1             -- error
   end if
   return {lBound, uBound, repeat(initVal, uBound-lBound+1)}
end function

global function array_put (sequence array, integer index, object val)
   -- write to an one-dimensional 'array' with arbitrary bounds
   integer lBound
   lBound = array[LBOUND]
   if index < lBound or array[UBOUND] < index then
      return -1             -- error
   end if
   array[3][index-lBound+1] = val
   return array
end function

global function array_get (sequence array, integer index)
   -- read from an one-dimensional 'array' with arbitrary bounds
   integer lBound
   lBound = array[LBOUND]
   if index < lBound or array[UBOUND] < index then
      return -1             -- error
   end if
   return array[3][index-lBound+1]
end function


---+++  demo  +++---
include misc.e
sequence who

who = array_dim({2000, 2002}, "")
puts(1, "Our 'array':\n")
pretty_print(1, who, {3})

who = array_put(who, 2000, "Kim Dae-jung")
who = array_put(who, 2001, "United Nations, Kofi Annan")
who = array_put(who, 2002, "Jimmy Carter")

puts(1, "\nRecent Nobel Prices for Peace:\n")
for year = 2000 to 2002 do
   printf(1, "%d: %s\n", {year, array_get(who, year)})
end for
------------------------------[ end code ]------------------------------


In August 2002, there was also a discussion about arrays on this list.
Derek provided code for creating (1-based) multi-dimensional 'arrays',
that looked like this:

-----------------------------[ begin code ]-----------------------------
global function dim_array (sequence dimension, object init_value)
   -- example: sequence a
   --          a = dim_array({3,7,4}, 0)
   object array

   if length(dimension) = 0 then
      return 0     -- error
   end if

   array = init_value
   for i = length(dimension) to 1 by -1 do
      if atom(dimension[i]) and dimension[i] > 0 then
         array = repeat(array, dimension[i])
      else
         return i  -- error
      end if
   end for

   return array
end function
------------------------------[ end code ]------------------------------


If you combine both approaches, you'll have code for handling
multi-dimensional arrays with (almost) arbitrary bounds. 

Best regards,
   Juergen

-- 
 /"\  ASCII ribbon campain  |    |\      _,,,---,,_
 \ /  against HTML in       |    /,`.-'`'    -.  ;-;;,_
  X   e-mail and news,      |   |,4-  ) )-,_..;\ (  `'-'
 / \  and unneeded MIME     |  '---''(_/--'  `-'\_)