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test_delete.sol

pragma solidity >=0.4.0 <0.6.0;
contract DeleteExample {
    uint data;
    uint[] dataArray;
    
    function f() public {
        uint x = data;
        delete x; //sets x to 0, does not affect data
        delete data; // sets data to 0, does not affect x
        uint[] storage y = dataArray;
        delete dataArray; // this sets dataArray.length to zero, but as uint[] is a complex object, also
                            // y is affected which is an alias to the storage object
                            // On the other hand: "delete y" is not valid, as assignments to local variables
                            // referencing storage objects can only be made from existing storage objects.
        assert(y.length==0);
    }
}