Given that ptr points to an int, that vec is a vector<int>, and that ival is an int, explain the behavior of each of these expressions

(a) `ptr != 0 && *ptr++`

The expression means if `ptr` is not null pointer, then point to whatever next in memory and return a copy of the value of the original `int` variable. Since we don't know what next in memory is, it will be an error if we dereference `ptr` after the expression. The expression may be:

    ptr != 0 && (*ptr)++

(b) `ival++ && ival`

The expression first increases the value of `ival` and return a copy of the original value, then if the original value is nonzero, the right hand operand `ival`(the incremented one) is evaluated, if it is also nonzero, the expression is `true`, else it is `false.

(c) `vec[ival++] <= vec[ival]`

The order of evaluation of `<=` operator's operands is undefined. The expression should be:

    ++ival, vec[ival] <= vec[ival + 1]