[英]how to operate unique with “with” operator in systemverilog
I am a systemverilog user and I have faced a strange (from my point of view) behavior of combination of unique method called for fixed array with "with" clause.我是一个 systemverilog 用户,我遇到了一个奇怪的(从我的角度来看)结合使用固定数组的独特方法与“with”子句的行为。
module tb;
int array[9] = '{4, 7, 2, 5, 7, 1, 6, 3, 1};
int res[$];
initial begin
res = array.unique(x) with (x <= 3);
$display ("unique : %p", res);
end
endmodule
I've expected to get queue {2,1,3} but instead I have got {4,2}.我希望得到队列 {2,1,3},但我得到了 {4,2}。
I can't understand Why there is a one at the index 0?我不明白为什么在索引 0 处有一个? and Why are 2 and 3 missing from the result?
为什么结果中缺少 2 和 3?
Let me explain the result you were getting.让我解释一下你得到的结果。
The with
clause of the unique
method defines the expression used to determine uniqueness . unique
方法的with
子句定义了用于确定唯一性的表达式。 It will delete all but one arbitrary element from the set of elements having matching expressions.它将从具有匹配表达式的元素集中删除除一个任意元素之外的所有元素。
Since you chose an expression having a result of 1'b0 or 1'b1, it chose one out of the four elements (2, 1, 3, 1) where x <= 3
was true (2), and one out of the five elements (4, 7, 5, 7, 6) where it was false (4).由于您选择了结果为 1'b0 或 1'b1 的表达式,因此它选择了
x <= 3
为真 (2) 的四个元素 (2, 1, 3, 1) 中的一个,以及五个元素 (4, 7, 5, 7, 6) 是错误的 (4)。
You are trying to combine the find
method with the unique
method in a single operation.您正试图在单个操作中将
find
方法与unique
方法结合起来。 It doesn't work that way.它不是那样工作的。 You have to do it in two separate operations:
您必须在两个单独的操作中执行此操作:
module tb;
int array[9] = '{4, 7, 2, 5, 7, 1, 6, 3, 1};
int res[$];
initial begin
res = array.find(x) with (x <= 3);
res = res.unique;
$display ("unique : %p", res);
end
endmodule
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