diff --git a/exercises/18_iterators/iterators2.rs b/exercises/18_iterators/iterators2.rs index 8d8909bf..5903e657 100644 --- a/exercises/18_iterators/iterators2.rs +++ b/exercises/18_iterators/iterators2.rs @@ -1,31 +1,28 @@ // In this exercise, you'll learn some of the unique advantages that iterators -// can offer. Follow the steps to complete the exercise. +// can offer. -// Step 1. -// Complete the `capitalize_first` function. +// TODO: Complete the `capitalize_first` function. // "hello" -> "Hello" fn capitalize_first(input: &str) -> String { - let mut c = input.chars(); - match c.next() { + let mut chars = input.chars(); + match chars.next() { None => String::new(), - Some(first) => ???, + Some(first) => todo!(), } } -// Step 2. -// Apply the `capitalize_first` function to a slice of string slices. +// TODO: Apply the `capitalize_first` function to a slice of string slices. // Return a vector of strings. // ["hello", "world"] -> ["Hello", "World"] fn capitalize_words_vector(words: &[&str]) -> Vec { - vec![] + // ??? } -// Step 3. -// Apply the `capitalize_first` function again to a slice of string slices. -// Return a single string. +// TODO: Apply the `capitalize_first` function again to a slice of string +// slices. Return a single string. // ["hello", " ", "world"] -> "Hello World" fn capitalize_words_string(words: &[&str]) -> String { - String::new() + // ??? } fn main() { diff --git a/rustlings-macros/info.toml b/rustlings-macros/info.toml index 5e939867..5a337888 100644 --- a/rustlings-macros/info.toml +++ b/rustlings-macros/info.toml @@ -894,7 +894,7 @@ https://doc.rust-lang.org/std/iter/trait.Iterator.html""" name = "iterators2" dir = "18_iterators" hint = """ -Step 1: +`capitalize_first`: The variable `first` is a `char`. It needs to be capitalized and added to the remaining characters in `c` in order to return the correct `String`. @@ -905,12 +905,15 @@ The remaining characters in `c` can be viewed as a string slice using the The documentation for `char` contains many useful methods. https://doc.rust-lang.org/std/primitive.char.html -Step 2: +Use `char::to_uppercase`. It returns an iterator that can be converted to a +`String`. + +`capitalize_words_vector`: Create an iterator from the slice. Transform the iterated values by applying the `capitalize_first` function. Remember to `collect` the iterator. -Step 3: +`capitalize_words_string`: This is surprisingly similar to the previous solution. `collect` is very powerful and very general. Rust just needs to know the desired type.""" diff --git a/solutions/18_iterators/iterators2.rs b/solutions/18_iterators/iterators2.rs index 4e181989..db05f293 100644 --- a/solutions/18_iterators/iterators2.rs +++ b/solutions/18_iterators/iterators2.rs @@ -1 +1,56 @@ -// Solutions will be available before the stable release. Thank you for testing the beta version 🥰 +// In this exercise, you'll learn some of the unique advantages that iterators +// can offer. + +// "hello" -> "Hello" +fn capitalize_first(input: &str) -> String { + let mut chars = input.chars(); + match chars.next() { + None => String::new(), + Some(first) => first.to_uppercase().to_string() + chars.as_str(), + } +} + +// Apply the `capitalize_first` function to a slice of string slices. +// Return a vector of strings. +// ["hello", "world"] -> ["Hello", "World"] +fn capitalize_words_vector(words: &[&str]) -> Vec { + words.iter().map(|word| capitalize_first(word)).collect() +} + +// Apply the `capitalize_first` function again to a slice of string +// slices. Return a single string. +// ["hello", " ", "world"] -> "Hello World" +fn capitalize_words_string(words: &[&str]) -> String { + words.iter().map(|word| capitalize_first(word)).collect() +} + +fn main() { + // You can optionally experiment here. +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn test_success() { + assert_eq!(capitalize_first("hello"), "Hello"); + } + + #[test] + fn test_empty() { + assert_eq!(capitalize_first(""), ""); + } + + #[test] + fn test_iterate_string_vec() { + let words = vec!["hello", "world"]; + assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]); + } + + #[test] + fn test_iterate_into_string() { + let words = vec!["hello", " ", "world"]; + assert_eq!(capitalize_words_string(&words), "Hello World"); + } +}