Comparisons

Comparisons are a common way of generating a boolean value in your code. These expressions allow you to compare two values and determine the truth of a given condition. For example, the expression area > 23.5 is asking if the value in the area variable is larger than 23.5. The result of this expression will be either true or false depending on the current value stored in area. The table below lists some example values for this expression, given different values stored in the area variable.

Value in area	area > 23.5
73.2	true
-2.5	false
23.5	false
23.501	true

Programming languages offer a range of different comparison operators. These typically include comparisons to check if values are the same or different, and to check if one value is larger or small than another. The different operators for C# are listed in the following table.

Kind	Description	Operator
Equal	Are the values the same?	==
Not Equal	Are the values different?	!=
Larger Than	Is the left value larger than the right?	>
Less Than	Is the left value smaller than the right?	<
Larger Or Equal	Is the left value larger than or equal to the right?	>=
Less Or Equal	Is the left value smaller than or equal to the right?	<=

Tip

The symbols for less than, and larger than, can be seen visually. With less than, notice how the < character starts as a small point on the left and gets wider to the right. The left side is smaller than the right. In contrast, > starts wide and narrows to the point on the right, showing that the left side is larger than the right.

Caution

C# uses == for comparison and = for assignment. If you mix this up you may accidently be changing the value of a variable rather than comparing it.

Note

• Comparisons can only be performed between two values.
• The values on either side of the comparison are expressions, allowing you to calculate the values being compared.

Comparison — when, why, and how

Boolean values are core to control flow, and comparisons are the main tool you will use to generate these boolean values. As you think through the actions you want the computer to perform, you use these comparisons to make decisions and determine which actions are run. For example, you can ask the user for their name, then compare that name to your name in order to perform an action when the names match. Similarly, in a banking application you can check if an account balance is larger than, or equal to, the amount being withdrawn as part of the decision on how to respond to the user’s request.

Examples

• guess == target: does the guess equal the target?
• guess > target: is the guess larger than the target?
• guess <= target: is the guess smaller than, or equal to, the target?

You can also use comparisons for user interaction in SplashKit. For example, you could use the MouseX and MouseY SplashKit methods to compare the mouse’s position to the location of a button on the window.

• MouseX() > 50: is the mouse more than 50 pixels from the left of the window?
• MouseX() <= 75: is the mouse less than or equal to 75 pixels from the left of the window?

In order to determine if the mouse was over something like a button, we would need to be able to combine multiple boolean values together in meaningful ways. Logical operators allow us to do this, so let’s look at them next.