[SV]SystemVerilog關聯數組查找方法（ associative array find_index method）

                       Associative array find_index method

       SystemVerilog array Index finder method shall return single or multiple indexes which satisfies the condition.The condition also shall be single or multiple conditions. multiple conditions can be written on using conditional expressions. example: &&, || etc.

一、index finder methods

• find_index()               returns the indexes of all the elements satisfying the given expression
• find_first_index()      returns the index of the first element satisfying the given expression
• find_last_index()       returns the index of the last element satisfying the given expression
• unique_index()          returns the indexes of all elements with unique values or whose expression is unique‘with’ clause is optional for min,max,unique and unique_index methods

二、associative array find_index example

       Below example shows the return of single and multiple index return.

class packet;
  int a;
  int b;
   
  function void display();
    $display("\tValue of a = %0d",a);
    $display("\tValue of b = %0d",b);
  endfunction
endclass
 
 
module assoc_array;
   
  //declaration of array
  packet assoc_array[*];
  packet pkt;
  int    count,qu[$],tmp_var;
   
  initial begin
     
    pkt = new();
    pkt.a = 8;
    pkt.b = 3;
    assoc_array[2] = pkt;
     
    pkt = new();
    pkt.a = 0;
    pkt.b = 6;
    assoc_array[5] = pkt;
     
    pkt = new();
    pkt.a = 2;
    pkt.b = 6;
    assoc_array[6] = pkt;
         
    pkt = new();
    pkt.a = 1;
    pkt.b = 6;
    assoc_array[9] = pkt;
    //----------------------------------------------------------------------------
    //------- Find Index Method -------
    //----------------------------------------------------------------------------
     
    //Type-1: returning one matching index
    qu = assoc_array.find_index with (item.a == 'h2);
    count = qu.size();
     
    for(int i=0;i<count;i++) begin //{
      tmp_var = qu.pop_front();
      $display("Index of Asoc Array for a == 2 is %0d",tmp_var);
    end //}
     
    //Type-2: returning mutiple matching index
    qu = assoc_array.find_index with (item.b == 6);
    count = qu.size();
     
    for(int i=0;i<count;i++) begin //{
      tmp_var = qu.pop_front();
      $display("Index of Asoc Array for b == 6 is %0d",tmp_var);
    end //}
     
    //Type-3: with multiple conditions
    qu  = assoc_array.find_index with (item.a == 2 && item.b == 6);
    count = qu.size();
     
    for(int i=0;i<count;i++) begin //{
      tmp_var = qu.pop_front();
      $display("Index of Asoc Array for a == 2,  b == 6 is %0d",tmp_var);
    end //}
     
    //Type-4: with multiple conditions
    qu  = assoc_array.find_index with (item.a < 2 && item.b > 5);
    count = qu.size();
     
    for(int i=0;i<count;i++) begin //{
      tmp_var = qu.pop_front();
      $display("Index of Asoc Array for a < 2,  b > 5 is %0d",tmp_var);
    end //}
  end
endmodule

• Simulator Output 

Index of Asoc Array for a == 2 is 6
Index of Asoc Array for b == 6 is 5
Index of Asoc Array for b == 6 is 6
Index of Asoc Array for b == 6 is 9
Index of Asoc Array for a == 2, b == 6 is 6
Index of Asoc Array for a < 2, b > 5 is 5
Index of Asoc Array for a < 2, b > 5 is 9