Add code from the lecture

materialien/comma-list-iter.rs

@@ -0,0 +1,27 @@
+use std::str::FromStr;
+
+fn main() {
+    let res = parse_list("1, 2, 3; , ,7, 8,9; 6;3,5;");
+    println!("{:#?}", res);
+    let res = parse_list("1, peter, 3, 4");
+    println!("{:#?}", res);
+}
+
+// "1, 2, 3; 7, 8,9; 6;3,5;"
+fn parse_list(input: &str)
+    -> Result<Vec<Vec<u32>>, <u32 as FromStr>::Err>
+{
+    // The following code could be expressed even shorter, but this is the
+    // exact code as shown in the lecture.
+    input.split(';')
+        .map(|s| s.trim())
+        .filter(|s| !s.is_empty())
+        .map(|s| {
+            s.split(',')
+                .map(|s| s.trim())
+                .filter(|s| !s.is_empty())
+                .map(|s| s.parse())
+                .collect()
+        })
+        .collect()
+}