Ejercicios 57/94
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@ -5,14 +5,12 @@
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// construct to `Option` that can be used to express error conditions. Let's use it!
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// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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pub fn generate_nametag_text(name: String) -> Option<String> {
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pub fn generate_nametag_text(name: String) -> Result<String, String> {
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if name.is_empty() {
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// Empty names aren't allowed.
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None
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Err("`name` was empty; it must be nonempty.".to_string())
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} else {
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Some(format!("Hi! My name is {}", name))
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Ok(format!("Hi! My name is {}", name))
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}
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}
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@ -17,14 +17,12 @@
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// one is a lot shorter!
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// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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use std::num::ParseIntError;
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pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
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let processing_fee = 1;
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let cost_per_item = 5;
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let qty = item_quantity.parse::<i32>();
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let qty = item_quantity.parse::<i32>()?;
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Ok(qty * cost_per_item + processing_fee)
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}
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@ -4,11 +4,9 @@
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// Why not? What should we do to fix it?
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// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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use std::num::ParseIntError;
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fn main() {
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fn main() -> Result<(), ParseIntError> {
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let mut tokens = 100;
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let pretend_user_input = "8";
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@ -20,6 +18,7 @@ fn main() {
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tokens -= cost;
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println!("You now have {} tokens.", tokens);
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}
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Ok(())
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}
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pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
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@ -1,8 +1,6 @@
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// errors4.rs
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// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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#[derive(PartialEq, Debug)]
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struct PositiveNonzeroInteger(u64);
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@ -14,8 +12,13 @@ enum CreationError {
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impl PositiveNonzeroInteger {
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fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
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// Hmm...? Why is this only returning an Ok value?
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Ok(PositiveNonzeroInteger(value as u64))
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if value < 0 {
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Err(CreationError::Negative)
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} else if value == 0 {
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Err(CreationError::Zero)
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}else {
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Ok(PositiveNonzeroInteger(value as u64))
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}
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}
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}
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@ -16,14 +16,12 @@
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// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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use std::error;
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use std::fmt;
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use std::num::ParseIntError;
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// TODO: update the return type of `main()` to make this compile.
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fn main() -> Result<(), Box<dyn ???>> {
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fn main() -> Result<(), Box<dyn error::Error>> {
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let pretend_user_input = "42";
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let x: i64 = pretend_user_input.parse()?;
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println!("output={:?}", PositiveNonzeroInteger::new(x)?);
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@ -8,8 +8,6 @@
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// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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use std::num::ParseIntError;
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// This is a custom error type that we will be using in `parse_pos_nonzero()`.
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@ -23,14 +21,13 @@ impl ParsePosNonzeroError {
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fn from_creation(err: CreationError) -> ParsePosNonzeroError {
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ParsePosNonzeroError::Creation(err)
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}
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// TODO: add another error conversion function here.
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// fn from_parseint...
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fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
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ParsePosNonzeroError::ParseInt(err)
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}
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}
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fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
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// TODO: change this to return an appropriate error instead of panicking
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// when `parse()` returns an error.
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let x: i64 = s.parse().unwrap();
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let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
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PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
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}
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@ -1,16 +1,19 @@
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// options1.rs
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// Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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// This function returns how much icecream there is left in the fridge.
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// If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
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// all, so there'll be no more left :(
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fn maybe_icecream(time_of_day: u16) -> Option<u16> {
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// We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0
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// The Option output should gracefully handle cases where time_of_day > 23.
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// TODO: Complete the function body - remember to return an Option!
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???
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if time_of_day < 22 {
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Some(5)
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} else if time_of_day < 24 {
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Some(0)
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} else {
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None
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}
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}
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#[cfg(test)]
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@ -28,8 +31,7 @@ mod tests {
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#[test]
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fn raw_value() {
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// TODO: Fix this test. How do you get at the value contained in the Option?
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let icecreams = maybe_icecream(12);
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assert_eq!(icecreams, 5);
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assert_eq!(icecreams, Some(5));
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}
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}
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@ -1,8 +1,6 @@
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// options2.rs
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// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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#[cfg(test)]
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mod tests {
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#[test]
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@ -10,8 +8,7 @@ mod tests {
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let target = "rustlings";
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let optional_target = Some(target);
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// TODO: Make this an if let statement whose value is "Some" type
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word = optional_target {
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if let Some(word) = optional_target {
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assert_eq!(word, target);
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}
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}
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@ -24,10 +21,8 @@ mod tests {
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optional_integers.push(Some(i));
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}
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// TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
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// You can stack `Option<T>`'s into while let and if let
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integer = optional_integers.pop() {
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assert_eq!(integer, range);
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while let Some(integer) = optional_integers.pop() {
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assert_eq!(integer, Some(range));
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range -= 1;
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}
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}
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@ -1,8 +1,6 @@
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// options3.rs
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// Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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struct Point {
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x: i32,
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y: i32,
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let y: Option<Point> = Some(Point { x: 100, y: 200 });
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match y {
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Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
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Some(ref p) => println!("Co-ordinates are {},{} ", p.x, p.y),
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_ => println!("no match"),
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}
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y; // Fix without deleting this line.
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