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// iterators2.rs
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// In this module, you'll learn some of the unique advantages that iterators can offer.
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// Step 1. Complete the `capitalize_first` function to pass the first two cases.
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// Step 2. Apply the `capitalize_first` function to a vector of strings.
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// Ensure that it returns a vector of strings as well.
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// Step 3. Apply the `capitalize_first` function again to a list.
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// Try to ensure it returns a single string.
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// In this exercise, you'll learn some of the unique advantages that iterators
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// can offer. Follow the steps to complete the exercise.
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// As always, there are hints if you execute `rustlings hint iterators2`!
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// I AM NOT DONE
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// Step 1.
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// Complete the `capitalize_first` function.
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// "hello" -> "Hello"
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pub fn capitalize_first(input: &str) -> String {
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let mut c = input.chars();
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match c.next() {
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None => String::new(),
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Some(first) => first.collect::<String>() + c.as_str(),
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Some(first) => ???,
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}
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}
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// Step 2.
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// Apply the `capitalize_first` function to a slice of string slices.
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// Return a vector of strings.
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// ["hello", "world"] -> ["Hello", "World"]
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pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
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vec![]
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}
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// Step 3.
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// Apply the `capitalize_first` function again to a slice of string slices.
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// Return a single string.
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// ["hello", " ", "world"] -> "Hello World"
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pub fn capitalize_words_string(words: &[&str]) -> String {
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String::new()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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// Step 1.
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// Tests that verify your `capitalize_first` function implementation
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#[test]
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fn test_success() {
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assert_eq!(capitalize_first("hello"), "Hello");
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@ -33,18 +46,15 @@ mod tests {
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assert_eq!(capitalize_first(""), "");
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}
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// Step 2.
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#[test]
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fn test_iterate_string_vec() {
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let words = vec!["hello", "world"];
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let capitalized_words: Vec<String> = // TODO
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assert_eq!(capitalized_words, ["Hello", "World"]);
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assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
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}
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#[test]
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fn test_iterate_into_string() {
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let words = vec!["hello", " ", "world"];
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let capitalized_words = // TODO
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assert_eq!(capitalized_words, "Hello World");
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assert_eq!(capitalize_words_string(&words), "Hello World");
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}
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}
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19
info.toml
19
info.toml
@ -704,21 +704,20 @@ path = "exercises/standard_library_types/iterators2.rs"
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mode = "test"
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hint = """
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Step 1
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You need to call something on `first` before it can be collected
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Currently its type is `char`. Have a look at the methods that are available on that type:
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The variable `first` is a `char`. It needs to be capitalized and added to the
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remaining characters in `c` in order to return the correct `String`.
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The remaining characters in `c` can be viewed as a string slice using the
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`as_str` method.
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The documentation for `char` contains many useful methods.
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https://doc.rust-lang.org/std/primitive.char.html
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Step 2
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First you'll need to turn the Vec into an iterator
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Then you'll need to apply your function unto each item in the vector
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P.s. Don't forget to collect() at the end!
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Create an iterator from the slice. Transform the iterated values by applying
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the `capitalize_first` function. Remember to collect the iterator.
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Step 3.
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This is very similar to the previous test. The only real change is that you will need to
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alter the type that collect is coerced into. For a bonus you could try doing this with a
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turbofish"""
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This is surprising similar to the previous solution. Collect is very powerful
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and very general. Rust just needs to know the desired type."""
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[[exercises]]
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name = "iterators3"
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