Displaying associative array elements in Specific order

SystemVerilog
, ,
1

Hi All,

Consider the following code

bit [1:0] assoc[int];
int i;
    
initial begin    
     assoc[3] = 1;    
    assoc[10] = 0;    
     assoc[1] = 2;
    
    foreach(assoc[j]) 
      $display("assoc['d%0d] is 'd%0d",j,assoc[j]);
end

I observe that foreach iterates through the indexes of int type index of assoc in ascending order

i.e 1 → 3 → 10

Is there a way to iterate through assoc in descending order ? i.e 10 → 3 → 1

2

I tried using

for( assoc.last(i) ; i < assoc.size() ; assoc.prev(i) )                   
   $display("assoc['d%0d] is 'd%0d",i,assoc[i]);

However, this doesn’t compile. Any suggestions on how to make it work ?

My 2nd attempt worked but I am not sure why I don’t run into an infinite loop

void’( assoc.last(i) );
do begin
  $display("assoc['d%0d] is 'd%0d",i,assoc[i]);  
end while( assoc.prev(i) );

How does the while loop terminate ?

3

from the description of the prev() function from IEEE Std 1800-2023:

7.9.7 Prev()

The prev() function finds the largest index whose value is smaller than the given index argument. If there is a previous entry, the index variable is assigned the index of the previous entry, and the function returns 1.
Otherwise, the index is unchanged, and the function returns 0.

so when i is the smallest key in assoc the next call to assoc.prev(i) will return 0, and will result in the end of the loop.

A way to make it work with the for loop can be:

  for( int tmp = assoc.last(i) ; tmp ; tmp = assoc.prev(i) )
$display("assoc['d%0d] is 'd%0d",i,assoc[i]);
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