Comparison and Equality Functions in Clojure

Welcome back! Now that you have a solid grasp of logical functions, it's time to explore another vital aspect of programming in Clojure — comparison and equality functions. These are integral for making accurate decisions within your code. By building on the knowledge of conditionals and logical functions you already have, you'll be able to perform precise comparisons and check for equality effortlessly.

In this lesson, you will become proficient in using comparison and equality functions, enabling you to write more nuanced and sophisticated Clojure programs. Specifically, you'll learn about:

1. < (Less Than): Compares numbers to check if the sequence is in ascending order.
2. > (Greater Than): Compares numbers to check if the sequence is in descending order.
3. <= (Less Than or Equal To): Verifies if each number in a sequence is less than or equal to the following number.
4. >= (Greater Than or Equal To): Verifies if each number in a sequence is greater than or equal to the following number.
5. = (Equality): Checks if multiple values are identical.
6. == (Numeric Equality): Verifies numeric equivalency across different types.

Understanding these functions is crucial for tasks such as sorting data, validating user inputs, and much more.

Here is a glimpse of what you'll be able to do after completing this unit:

;; Using < (works with any number of arguments)
(println (< 1 2))               ;; true
(println (< 1 2 3 4))           ;; true
(println (< 1 2 2))             ;; false

;; Using = (works with any number of arguments)
(println (= 1 1))               ;; true
(println (= 1 1 1))             ;; true
(println (= 1 2))               ;; false

;; Single equals (=) vs Double equals (==)
(println (= 1 1/1 1N))          ;; true (all are equal)
(println (= 1 1.0M))            ;; false (different types)
(println (= 1/2 0.5))           ;; false (ratio vs floating point)

(println (== 1 1.0M 1.0 1))     ;; true (numerically equal)
(println (== 1 1.1))            ;; false (different values)
(println (== 1 1))              ;; true (same values)