No Operator Overloading: Code Examples

// C++: operator overloading
class Vec2 {
public:
  int x, y;
  Vec2(int ax, int ay) : x(ax), y(ay) {}
  Vec2 operator+(const Vec2& rhs) const { return Vec2(x + rhs.x, y + rhs.y); }
  bool operator==(const Vec2& rhs) const { return x == rhs.x && y == rhs.y; }
};

Vec2 c = Vec2(1, 2) + Vec2(3, 4);
bool same = (c == Vec2(4, 6));

// SystemVerilog: explicit methods
class vec2;
  int x, y;

  function new(int ax = 0, int ay = 0);
    x = ax;
    y = ay;
  endfunction

  function vec2 add(vec2 rhs);
    return new(x + rhs.x, y + rhs.y);
  endfunction

  function bit equals(vec2 rhs);
    return (x == rhs.x) && (y == rhs.y);
  endfunction
endclass

vec2 c_sv = new(1, 2);
c_sv = c_sv.add(new(3, 4));
if (c_sv.equals(new(4, 6))) $display("match");

// Java: equals/hashCode/compareTo contract on domain objects
class Txn implements Comparable<Txn> {
  int addr;
  int data;
  public boolean equals(Object o) {
    if (!(o instanceof Txn)) return false;
    Txn rhs = (Txn)o;
    return addr == rhs.addr && data == rhs.data;
  }
  public int hashCode() { return 31 * addr + data; }
  public int compareTo(Txn rhs) { return Integer.compare(addr, rhs.addr); }
}

// SystemVerilog: named methods with explicit intent
class txn;
  rand int addr;
  rand int data;

  function bit equals(txn rhs);
    return (addr == rhs.addr) && (data == rhs.data);
  endfunction

  function int compare(txn rhs);
    if (addr < rhs.addr) return -1;
    if (addr > rhs.addr) return 1;
    return 0;
  endfunction

  function int unsigned hash();
    return (addr * 32'd31) ^ data;
  endfunction
endclass