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100 lines
3 KiB
Rust
100 lines
3 KiB
Rust
// Let's build a little machine in the form of a function. As input, we're going
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// to give a list of strings and commands. These commands determine what action
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// is going to be applied to the string. It can either be:
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// - Uppercase the string
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// - Trim the string
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// - Append "bar" to the string a specified amount of times
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//
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// The exact form of this will be:
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// - The input is going to be a vector of a 2-length tuple,
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// the first element is the string, the second one is the command.
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// - The output element is going to be a vector of strings.
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enum Command {
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Uppercase,
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Trim,
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Append(usize),
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}
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mod my_module {
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use super::Command;
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// The solution with a loop. Check out `transformer_iter` for a version
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// with iterators.
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pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
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let mut output = Vec::new();
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for (mut string, command) in input {
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// Create the new string.
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let new_string = match command {
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Command::Uppercase => string.to_uppercase(),
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Command::Trim => string.trim().to_string(),
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Command::Append(n) => {
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for _ in 0..n {
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string += "bar";
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}
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string
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}
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};
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// Push the new string to the output vector.
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output.push(new_string);
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}
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output
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}
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// Equivalent to `transform` but uses an iterator instead of a loop for
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// comparison. Don't worry, we will practice iterators later ;)
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pub fn transformer_iter(input: Vec<(String, Command)>) -> Vec<String> {
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input
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.into_iter()
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.map(|(mut string, command)| match command {
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Command::Uppercase => string.to_uppercase(),
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Command::Trim => string.trim().to_string(),
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Command::Append(n) => {
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for _ in 0..n {
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string += "bar";
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}
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string
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}
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})
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.collect()
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}
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}
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fn main() {
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// You can optionally experiment here.
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}
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#[cfg(test)]
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mod tests {
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// Import `transformer`.
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use super::my_module::transformer;
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use super::my_module::transformer_iter;
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use super::Command;
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#[test]
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fn it_works() {
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for transformer in [transformer, transformer_iter] {
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let input = vec![
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("hello".to_string(), Command::Uppercase),
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(" all roads lead to rome! ".to_string(), Command::Trim),
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("foo".to_string(), Command::Append(1)),
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("bar".to_string(), Command::Append(5)),
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];
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let output = transformer(input);
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assert_eq!(
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output,
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[
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"HELLO",
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"all roads lead to rome!",
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"foobar",
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"barbarbarbarbarbar",
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]
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);
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}
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}
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}
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