Constraint question :: sum() with ( item.index .. )

SystemVerilog
,
5

In reply to dave_59:

Hi Dave ,

I was trying the above Sample Code using data type as ‘bit signed’ .
I see unexpected results with following code ::


class temp;
  rand bit signed [2:0] b4num[16];
 
  constraint e { 
                      b4num.sum with ( int'( ( item.index % 2 ) ? item : !item ) ) == 8 ; 
                       
               }   
endclass
 
 temp t ; 

 initial begin
       t = new();
        repeat(5)
          if ( t.randomize() )
          begin
        $display(" b4 is  %p", t.b4num);
        $display(" b4 Even sum is  %0d", t.b4num.sum() with (  int'( ( item.index % 2 ) ? 0 : !item ) )); 
        $display(" b4 Odd sum is  %0d",  t.b4num.sum() with (  int'( ( item.index % 2 ) ? item : 0 ) )); 
      end 
 end

The Output for the code is ::
**
b4 is '{1, 1, 3, -3, -2, 0, -3, 1, -4, 0, -1, 0, 2, 1, -2, 0}
b4 Even sum is 0
b4 Odd sum is 0
b4 is '{-3, 2, 1, 2, -2, 0, -2, 1, -1, 0, 1, 3, -3, 0, 1, 0}
b4 Even sum is 0
b4 Odd sum is 8
b4 is '{2, 1, 1, 0, 2, 2, -2, -4, -4, 0, 1, 0, 2, 1, 2, 0}
b4 Even sum is 0
b4 Odd sum is 0**

Only 2nd Output meets my expectations

I am not sure how 1st and 3rd Output satisfy the sum() Constraint to be 8