## Section1.29Worked Example: Swap

### Subgoals for evaluating an assignment statement.

1. Determine resultant data type of expression

2. Update variable for pre-increment or pre-decrement operators (side effect)

3. Evaluate arithmetic expression according to operator precedence

4. If an assignment statement (=), is Left Hand Side (LHS) a variable? Check data type of value against data type of variable.

5. Update variable for post-increment or post-decrement operators (side effect)

You can watch this video or read through the content below it.

Consider these declarations.

int x,y,z;
x = 7;
y = 13;


Now consider this code for swapping the values of x and y. Note the need for a third variable to hold the value of x so that it is not lost when assigning the value of y into x.

z = x;
x = y;
y = z;


The diagram below shows the changes in memory after executing each of the six lines of code.