Auto merge of #186 - Jesse-Cameron:iterator-exercise2, r=komaeda

feat(iterators2): adds iterators2 exercise including config

Hi there!

I really enjoyed doing the rustlings exercises so I thought that I would try to add an exercise!

This one just covers a couple of basic iterator operations. Getting people used to the `map` and `collect` functions.

However, it does feel kinda similar to the next exercise. So I may also revisit some of the tests in iterators3 if we think that is necessary.

exercises/standard_library_types/iterators2.rs

@@ -0,0 +1,145 @@
+// iterators2.rs
+// In this module, you'll learn some of unique advantages that iterators can offer
+// Step 1. Complete the `capitalize_first` function to pass the first two cases
+// Step 2. Apply the `capitalize_first` function to a vector of strings, ensuring that it
+// Step 3. Apply the `capitalize_first` function again to a list, but try and ensure it returns a single string
+// As always, there are hints below!
+
+pub fn capitalize_first(input: &str) -> String {
+    let mut c = input.chars();
+    match c.next() {
+        None => String::new(),
+        Some(first) => first.collect()::<String>() + c.as_str(),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // Step 1.
+    // Tests that verify your `capitalize_first` function implementation
+    #[test]
+    fn test_success() {
+        assert_eq!(capitalize_first("hello"), "Hello");
+    }
+
+    #[test]
+    fn test_empty() {
+        assert_eq!(capitalize_first(""), "");
+    }
+
+    // Step 2.
+    #[test]
+    fn test_iterate_string_vec() {
+        let words = vec!["hello", "world"];
+        let capitalized_words: Vec<String> = // TODO
+        assert_eq!(capitalized_words, ["Hello", "World"]);
+    }
+
+    #[test]
+    fn test_iterate_into_string() {
+        let words = vec!["hello", " ", "world"];
+        let capitalized_words = // TODO
+        assert_eq!(capitalized_words, "Hello World");
+    }
+}
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+// Step 1
+// You need to call something on `first` before it can be collected
+// Currently it's type is `char`. Have a look at the methods that are available on that type:
+// https://doc.rust-lang.org/std/primitive.char.html
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+// Step 2
+// First you'll need to turn the Vec into an iterator
+// Then you'll need to apply your function unto each item in the vector
+// P.s. Don't forget to collect() at the end!
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+// Step 3.
+// This is very similar to the previous test. The only real change is that you will need to
+// alter the type that collect is coerced into. For a bonus you could try doing this with a
+// turbofish

info.toml

@@ -210,6 +210,10 @@ mode = "compile"
 path = "exercises/standard_library_types/arc1.rs"
 mode = "compile"
 
+[[exercises]]
+path = "exercises/standard_library_types/iterators2.rs"
+mode = "test"
+
 [[exercises]]
 path = "exercises/standard_library_types/iterators3.rs"
 mode = "test"