<NA>
<NA>
function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        returns (bool)
    {
        uint256 oldValue = _allowance[msg.sender][spender];
        if (subtractedValue >= oldValue) {
            _allowance[msg.sender][spender] = 0;
        } else {
            _allowance[msg.sender][spender] = oldValue.sub(subtractedValue);
        }
        emit Approval(msg.sender, spender, _allowance[msg.sender][spender]);
        return true;
    }
/**
 * @dev Decrease the amount of tokens that an owner has allowed to a spender.
 *
 * @param spender The address which will spend the funds.
 * @param subtractedValue The amount of tokens to decrease the allowance by.
 */