Tutorial: Conditional Statements with "if

The if Conditional

When programming a computer, we often want a machine to make decisions automatically. For example, we might want the computer to add some numbers, then determine if the sum is greater than 10. Or, we might want a program to search the Internet and determine if a picture is a cat, or any number other reasons (e.g., self-driving cars should stop if there is a pedestrian in their way). Quorum uses the if construct for decision making, like many other programming languages. For example, suppose we wanted to test whether an integer is greater than 10. We would do this like so:

integer a = 11
if a > 10 
     output a
end
output "The end"

In this case, if a happens to be greater than 10, then Quorum will execute any computer code that is between the top line of the if and the "end" at the bottom. Sometimes, however, we want to test multiple conditions to see if any of them are true. We can do thise by using a construct called elseif, which only executes when the the statements previous to it were false and the current one is true. We use else just like we use if, except with a different word in the beginning. Here is an example:

integer a = 1
integer b = 1000
integer c = 0
if a > 100
     c = 1
elseif b = 100
     c = 2
end
output c

Similarly, we may want to take an operation if none of the if statements or elseif statements were true. In this case, we have a catch all we can use, called else. Like before, else executes a block of code in it, but in this case only when all previous if statement tests failed. Building on previous examples, we can use else like so:

integer a = 1
integer b = 1000
integer c = 0
if a > 100
     c = 1
elseif b = 100
     c = 2
else
     c = 3
end
output c

In this case, the above code will first test to see if a is greater than 100. If that is so, it will execute the statement c = 1. However, if the value of a is not greater than 100, the code will then test to see if b is greater than 100. If that is the case, c will be set to 2. If neither a, nor b, are greater than 100, c will be set to 3. With this code as a guide, practice using if statements in the development environment below.

Next Tutorial

In the next tutorial, we will discuss Lab 3.1, which describes how Conditionals work in Quorum..