fix mistakes 1/x

learnclj.clj

@@ -259,8 +259,7 @@ nil          ; => nil (Null/Nothing)
 
 (swap! counter inc)     ; => 1
 (swap! counter + 5)     ; => 6
-(dosync
-  (reset! counter 0))   ; => 0
+(reset! counter 0)      ; => 0
 
 ;; --- 14. Java Interop ---
 
@@ -317,9 +316,21 @@ nil          ; => nil (Null/Nothing)
 
 ;; --- 18. Common Patterns ---
 
-;; Compose functions
-(defn make-upper [s] (str/upper-case s))
-(def make-upper-lower (comp str/lower-case str/upper-case))  ; => #object[clojure.core$comp$fn ...]
+;; Compose functions — comp reads right-to-left (like math)
+;; Example: slugify — find word chunks, lowercase, join with dashes
+(def slugify (comp #(str/join "-" %) #(mapv str/lower-case %) #(re-seq #"\S+" %)))
+
+;; Usage
+(slugify "  Hello World  ")  ; => "hello-world"
+(slugify "Foo Bar Baz")      ; => "foo-bar-baz"
+(slugify "  Hello  World  ") ; => "hello-world"
+
+;; Another: trim then uppercase
+(def trim->upper (comp str/upper-case str/trim))
+
+;; Usage
+(trim->upper "  hello  ")  ; => "HELLO"
+(trim->upper "  Clojure is fun  ")  ; => "CLOJURE IS FUN"
 
 ;; Partial application