first(), next() methods in associative array in systemverilog

Question

i wrote a simple code for testing different methods in array. here is the code:

module assoc_arr;
 int temp,imem[*];
 initial
 begin
  imem[ 2'd3 ] = 1;
  imem[ 16'hffff ] = 2;
  imem[ 4'b1000 ] = 3;
  if(imem.first(temp))
   $display(" First entry is at index %0db ",temp);
  if(imem.next(temp))
   $display(" Next entry is at index %0h after the index 3",temp);
// To print all the elements alone with its indexs
  if (imem.first(temp) )
   do
    $display( "%d : %d", temp, imem[temp] );
   while ( imem.next(temp) );
 end
endmodule

here there is a warning :: "Using indicated method on wildcard associative arrays is non standard." at imem.first(temp) and imem.next(temp).

why this warning is showing??

dwikle · Accepted Answer · 2013-07-29 13:17:12Z

4

Because it is not allowed by the language specification. From section 7.9.4 of the 1800-2012 SystemVerilog spec.

The syntax for the first() method is as follows:

function int first( ref index );

where index is an index of the appropriate type for the array in question. Associative arrays that specify a wildcard index type shall not be allowed.

You can download the language reference here:

http://standards.ieee.org/getieee/1800/download/1800-2012.pdf

I believe if you change your example to use a non-wildcard array it will work and you won't get the warning.

Example:

int temp[bit[15:0]];

edited Jul 29, 2013 at 13:17

answered Jul 29, 2013 at 13:09

dwikle

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1 Comment

biren.K Over a year ago

hi, i changed my code and wrote ` int temp[temp[15:0]]`. but it showed error.

jclin · Accepted Answer · 2013-07-30 09:06:01Z

0

If your associative array's key is always and only integer type, you can declare it as follows

int temp,imem[int];

Then your code should be able to run with first() and next() methods.

answered Jul 30, 2013 at 9:06

jclin

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2 Comments

biren.K Over a year ago

hi, i wrote like above one. but it showed error as: ref formal and actual do not have equivalent data types (expecting datatype compatible with 'int' but found 'integer' instead).

jclin Over a year ago

May I know the simulator you are using now? I use VCS and your original code can run correctly (but LRM denies such usage for wildcard index). If I use IUS, I have to modify your code to int temp, imem[int];. Or you may try to change all int to integer type (2-value V.S 4-value) and try again.

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