Range Over Built in Verilog

Here we use range to sum the numbers in a slice. Arrays work like this too.

module range_example;
  initial begin
    // Define the array
    integer nums[0:2];
    nums[0] = 2;
    nums[1] = 3;
    nums[2] = 4;
    
    // Sum the array elements
    integer sum;
    integer i;
    sum = 0;
    for (i = 0; i <= 2; i = i + 1) begin
      sum = sum + nums[i];
    end
    $display("sum: %d", sum);
  end
endmodule

range on arrays and slices provides both the index and value for each entry. Above we didn’t need the index, so we ignored it. Sometimes we actually want the indexes though.

module range_with_index_example;
  initial begin
    // Define the array
    integer nums[0:2];
    nums[0] = 2;
    nums[1] = 3;
    nums[2] = 4;
    
    // Print the index where the value is 3
    integer i;
    for (i = 0; i <= 2; i = i + 1) begin
      if (nums[i] == 3) begin
        $display("index: %d", i);
      end
    end
  end
endmodule

range on map iterates over key/value pairs.

module range_map_example;
  initial begin
    // Define the associative array (map)
    string kvs[string];
    kvs["a"] = "apple";
    kvs["b"] = "banana";
    
    // Iterate over the map
    string key;
    foreach (kvs[key]) begin
      $display("%s -> %s", key, kvs[key]);
    end
  end
endmodule

range can also iterate over just the keys of a map.

module range_map_keys_example;
  initial begin
    // Define the associative array (map)
    string kvs[string];
    kvs["a"] = "apple";
    kvs["b"] = "banana";
    
    // Iterate over just the keys
    string key;
    foreach (kvs[key]) begin
      $display("key: %s", key);
    end
  end
endmodule

range on strings iterates over Unicode code points. The first value is the starting byte index of the rune and the second the rune itself.

module range_string_example;
  initial begin
    // Define the string
    string word;
    word = "go";
    
    // Iterate over the string
    integer i;
    for (i = 0; i < $size(word); i = i + 1) begin
      $display("%d %d", i, word[i*8+:8]);
    end
  end
endmodule

Now that we understand how to use range with arrays, slices, maps, and strings, let’s explore more about the language.

Recursion in Verilog

Pointers in Verilog

Learn X By Example

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Range Over Built in Verilog