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From: "digi_cs" <cosmogen@gmail.com>
Subject: HID: LIST - list array
Newsgroups: comp.lang.awk
Date: Thu, 17 Oct 2024 07:54:20 +0300
Lines: 46
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HID: LIST

@include “github.com/digics/UID10/uid.lib”      

LIST = hid::get( “LIST” )

An array (A) in AWK can represent a list of unique items with an undefined order.
To introduce the concept of an array with a defined sequence of its indexes (items),
we need to specify this sequence in a subarray A[LIST] as a simple list. 

      # items of A: first, next and last:
      
      A[ “LIST” ][ “” ] = “first”
                 [ “first” ] = “next”
                 [ “next” ] = “last”
                 [ “last” [ = “”
       [ “first” ]...
       [ “next” ]...
       [ “last” ]...

Thus, instead of a for-in loop for array A, we use: 

            i = “”
            while ( “” != i = A[ LIST][ i ] )

                  # process A[ i ]

            or

            for ( i = “”; “” != i = A[ LIST ][ i ]; ) 

                  # process A[ i ]

At the same time, we can still work with the main array in a for-in loop — with one caveat: 

            for ( i in A )
                  if ( i in HID )
                        continue          # this is hid (LIST)
                  else
                        # process A[ i ]


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