lecture 02

lectures/02/errors.rs

@@ -0,0 +1,35 @@
+fn test1() {
+    let x = Some(32);
+    println!("{}", x.unwrap());
+    // let x: Option<i32> = None;
+    // println!("{}", x.unrwap()); // panics
+
+    let n = "123".parse::<i32>();
+    println!("{n:?}")
+}
+
+fn sqrt(x: f64) -> Option<f64> {
+    if (x < 0.0) { None } else { Some(f64::sqrt(x)) }
+}
+
+fn ln_sqrt(x: f64) -> Option<f64> {
+    /*
+    match sqrt(x) {
+        Some(x) => f64::ln(x),
+        None => None,
+    }
+
+    // OR
+    if let Some(x) = sqrt(x) {
+        Some(f64::ln(x))
+    } else {
+        None
+    }
+     */
+
+    Some(f64::ln(sqrt(x)?))
+}
+
+fn main() {
+    test1();
+}