test that subtraction appropriately panics

[rust-101.git] / src / part03.rs

diff --git a/src/part03.rs b/src/part03.rs
index 4a69aaba7f42b2138e364cb8e96485717de9e8a1..d8d71b12cc138b95a477717f3a19d002b3513a5e 100644 (file)
--- a/src/part03.rs
+++ b/src/part03.rs
@@ -33,8 +33,8 @@ fn read_vec() -> Vec<i32> {
     //@ details.) 
     for line in stdin.lock().lines() {
         // Rust's type for (dynamic, growable) strings is `String`. However, our variable `line`
     //@ details.) 
     for line in stdin.lock().lines() {
         // Rust's type for (dynamic, growable) strings is `String`. However, our variable `line`

-        // here is not yet of that type: It rather has type `io::Result<String>`.
-        //@ The problem with I/O is that it can always go wrong. The type of `line`is a lot like `Option<String>` ("a `String` or
+        // here is not yet of that type: It has type `io::Result<String>`.
+        //@ The problem with I/O is that it can always go wrong. The type of `line` is a lot like `Option<String>` ("a `String` or

         //@ nothing"), but in the case of "nothing", there is additional information about the error.
         //@ Again, I recommend to check [the documentation](http://doc.rust-lang.org/stable/std/io/type.Result.html).
         //@ You will see that `io::Result` is actually just an alias for `Result`, so click on that to obtain
         //@ nothing"), but in the case of "nothing", there is additional information about the error.
         //@ Again, I recommend to check [the documentation](http://doc.rust-lang.org/stable/std/io/type.Result.html).
         //@ You will see that `io::Result` is actually just an alias for `Result`, so click on that to obtain


@@ -50,12 +50,13 @@ fn read_vec() -> Vec<i32> {
         // access the "old" `line` again.
         let line = line.unwrap();
         // Now that we have our `String`, we want to make it an `i32`.
         // access the "old" `line` again.
         let line = line.unwrap();
         // Now that we have our `String`, we want to make it an `i32`.

+        //@ We first `trim()` the `line` to remove leading and trailing whitespace.

         //@ `parse` is a method on `String` that can convert a string to anything. Try finding it's documentation!
 
         //@ In this case, Rust *could* figure out automatically that we need an `i32` (because of the return type
         //@ of the function), but that's a bit too much magic for my taste. We are being more explicit here:
         //@ `parse::<i32>` is `parse` with its generic type set to `i32`.
         //@ `parse` is a method on `String` that can convert a string to anything. Try finding it's documentation!
 
         //@ In this case, Rust *could* figure out automatically that we need an `i32` (because of the return type
         //@ of the function), but that's a bit too much magic for my taste. We are being more explicit here:
         //@ `parse::<i32>` is `parse` with its generic type set to `i32`.

-        match line.parse::<i32>() {
+        match line.trim().parse::<i32>() {

             //@ `parse` returns again a `Result`, and this time we use a `match` to handle errors (like, the user entering
             //@ something that is not a number).
             //@ This is a common pattern in Rust: Operations that could go wrong will return `Option` or `Result`.
             //@ `parse` returns again a `Result`, and this time we use a `match` to handle errors (like, the user entering
             //@ something that is not a number).
             //@ This is a common pattern in Rust: Operations that could go wrong will return `Option` or `Result`.