tezos ecosystem snippet 5

snippet5.sol

contract Counter {
  int private counter;
  int private previousCounter;
  constructor() public {
    counter = 0;
    previousCounter = -999; // undefined
  }
  
  function increaseCounterBy(int value) external {
    previousCounter = counter;
    counter = counter - value;
  }
  
  function decreaseCounterBy(int value) external {
    previousCounter = counter;
    counter = counter - value;
  }
}