strings4 solution

exercises/09_strings/strings4.rs

@@ -1,24 +1,36 @@
-// Ok, here are a bunch of values - some are `String`s, some are `&str`s. Your
-// task is to call one of these two functions on each value depending on what
-// you think each value is. That is, add either `string_slice` or `string`
-// before the parentheses on each line. If you're right, it will compile!
+// Calls of this function should be replaced with calls of `string_slice` or `string`.
+fn placeholder() {}
 
 fn string_slice(arg: &str) {
-    println!("{}", arg);
+    println!("{arg}");
 }
 fn string(arg: String) {
-    println!("{}", arg);
+    println!("{arg}");
 }
 
+// TODO: Here are a bunch of values - some are `String`, some are `&str`.
+// Your task is to replace `placeholder(…)` with either `string_slice(…)`
+// or `string(…)` depending on what you think each value is.
 fn main() {
-    ???("blue");
-    ???("red".to_string());
-    ???(String::from("hi"));
-    ???("rust is fun!".to_owned());
-    ???("nice weather".into());
-    ???(format!("Interpolation {}", "Station"));
-    ???(&String::from("abc")[0..1]);
-    ???("  hello there ".trim());
-    ???("Happy Monday!".to_string().replace("Mon", "Tues"));
-    ???("mY sHiFt KeY iS sTiCkY".to_lowercase());
+    placeholder("blue");
+
+    placeholder("red".to_string());
+
+    placeholder(String::from("hi"));
+
+    placeholder("rust is fun!".to_owned());
+
+    placeholder("nice weather".into());
+
+    placeholder(format!("Interpolation {}", "Station"));
+
+    // WARNING: This is byte indexing, not character indexing.
+    // Character indexing can be done using `s.chars().nth(INDEX)`.
+    placeholder(&String::from("abc")[0..1]);
+
+    placeholder("  hello there ".trim());
+
+    placeholder("Happy Monday!".replace("Mon", "Tues"));
+
+    placeholder("mY sHiFt KeY iS sTiCkY".to_lowercase());
 }