Beginner's Guide to Expressions in Ruby
Ruby uses the == operator for comparing two objects.
Let us try a simple exercise: write an expression that checks whether the value of the variable name is "Bob":
The other usual operators like greater than (>), less than (<), greater than or equal to (>=) etc. are supported.
The next exercise is to write an expression that validates whether age is less than or equal to 35.
Boolean expressions like the above always return either the true or false
objects.
Combining Expressions using the && and || operators
You can use the keywords || (read as 'or'), && (read as 'and') to combine expressions.
Try modifying the following expression to check whether age is greater than or equal
to 23 and the name is either Bob or Jill.
Just like the order of operations in mathematical expressions (PEMDAS anybody?), Ruby also has a set of laws governing the precedence of its various operators. However it is not something you need to be concerned about for now. Just make sure to use parentheses generously so that the order of operation is unambiguous to Ruby as well as for someone reading your code.
Negating expressions
Ruby lets you negate expressions using the ! operator (read as 'not').
For instance, ! (name == 'Jill') will return false if the name is Jill and
true for any other name.
Now try writing a simple expression that accepts any name except Bob
Awesome! Now that you've learned the basics of writing boolean expressions in Ruby, let us see how we can use them to decide the flow of our application in the next lesson.