11.函数原型有参数时需要填写对应参数进行调用
这里原先call_me函数没有填写参数导致报错 添加一个usize即可
rust
// functions3.rs
// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
fn main() {
call_me(10);
}
fn call_me(num: u32) {
for i in 0..num {
println!("Ring! Call number {}", i + 1);
}
}12.函数需要返回值
fn sale_price(price: i32) -> i32前面括号内是传入参数类型,后面是返回值类型
rust
// functions4.rs
// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a hint.
// This store is having a sale where if the price is an even number, you get
// 10 Rustbucks off, but if it's an odd number, it's 3 Rustbucks off.
// (Don't worry about the function bodies themselves, we're only interested
// in the signatures for now. If anything, this is a good way to peek ahead
// to future exercises!)
fn main() {
let original_price = 51;
println!("Your sale price is {}", sale_price(original_price));
}
fn sale_price(price: i32) -> i32{
if is_even(price) {
price - 10
} else {
price - 3
}
}
fn is_even(num: i32) -> bool {
num % 2 == 0
}13.函数隐式返回,不能使用逗号作为默认返回
这里square函数隐式返回num*num,如果加上分号会返回()
rust
// functions5.rs
// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a hint.
// I AM NOT DONE
fn main() {
let answer = square(3);
println!("The square of 3 is {}", answer);
}
fn square(num: i32) -> i32 {
num * num
}14.使用if编写函数功能
这里使用if判断a>b的情况 然后分情况讨论
rust
// if1.rs
// Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.
pub fn bigger(a: i32, b: i32) -> i32 {
// Complete this function to return the bigger number!
// Do not use:
// - another function call
// - additional variables
if a>b {
a
}
else {
b
}
}
// Don't mind this for now :)
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn ten_is_bigger_than_eight() {
assert_eq!(10, bigger(10, 8));
}
#[test]
fn fortytwo_is_bigger_than_thirtytwo() {
assert_eq!(42, bigger(32, 42));
}
}15.嵌套if返回条件
rust
// if2.rs
// Step 1: Make me compile!
// Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
// Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.
pub fn foo_if_fizz(fizzish: &str) -> &str {
if fizzish == "fizz" {
"foo"
} else {
if fizzish =="fuzz"{
"bar"
}
else {
"baz"
}
}
}
// No test changes needed!
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn foo_for_fizz() {
assert_eq!(foo_if_fizz("fizz"), "foo")
}
#[test]
fn bar_for_fuzz() {
assert_eq!(foo_if_fizz("fuzz"), "bar")
}
#[test]
fn default_to_baz() {
assert_eq!(foo_if_fizz("literally anything"), "baz")
}
}其中assert_eq!(a,b)是在比较a,b两个数值是否相等,用于做单元测试
16.使用if进行简单应用场景功能实现
自己编写calculate_price_of_apples(price:i32)->i32即可
rust
// quiz1.rs
// This is a quiz for the following sections:
// - Variables
// - Functions
// - If
// Mary is buying apples. The price of an apple is calculated as follows:
// - An apple costs 2 rustbucks.
// - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
// Write a function that calculates the price of an order of apples given
// the quantity bought. No hints this time!
// Put your function here!
fn calculate_price_of_apples(price:i32)->i32 {
if (price<=40){
return price*2;
}
return price;
}
// Don't modify this function!
#[test]
fn verify_test() {
let price1 = calculate_price_of_apples(35);
let price2 = calculate_price_of_apples(40);
let price3 = calculate_price_of_apples(41);
let price4 = calculate_price_of_apples(65);
assert_eq!(70, price1);
assert_eq!(80, price2);
assert_eq!(41, price3);
assert_eq!(65, price4);
}17.利用boolean类型变量做判断
rust
// primitive_types1.rs
// Fill in the rest of the line that has code missing!
// No hints, there's no tricks, just get used to typing these :)
fn main() {
// Booleans (`bool`)
let is_morning = true;
if is_morning {
println!("Good morning!");
}
let is_evening = false;
// let // Finish the rest of this line like the example! Or make it be false!
if is_evening {
println!("Good evening!");
}
}18.判断字符类型
我们在这里只需要填一个字符即可,即使是emjoy
rust
// primitive_types2.rs
// Fill in the rest of the line that has code missing!
// No hints, there's no tricks, just get used to typing these :)
fn main() {
// Characters (`char`)
// Note the _single_ quotes, these are different from the double quotes
// you've been seeing around.
let my_first_initial = 'C';
if my_first_initial.is_alphabetic() {
println!("Alphabetical!");
} else if my_first_initial.is_numeric() {
println!("Numerical!");
} else {
println!("Neither alphabetic nor numeric!");
}
let your_character='u';// Finish this line like the example! What's your favorite character?
// Try a letter, try a number, try a special character, try a character
// from a different language than your own, try an emoji!
if your_character.is_alphabetic() {
println!("Alphabetical!");
} else if your_character.is_numeric() {
println!("Numerical!");
} else {
println!("Neither alphabetic nor numeric!");
}
}19.获取字符串长度
rust
// primitive_types3.rs
// Create an array with at least 100 elements in it where the ??? is.
// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand for a hint.
fn main() {
let a = "99999999999999999999999999999999";
if a.len() >= 100 {
println!("Wow, that's a big array!");
} else {
println!("Meh, I eat arrays like that for breakfast.");
}
}20.字符串切片
使用&引用变量 [leftIndex..rightIndex)区间内切片
rust
// primitive_types4.rs
// Get a slice out of Array a where the ??? is so that the test passes.
// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand for a hint.
#[test]
fn slice_out_of_array() {
let a = [1, 2, 3, 4, 5];
let nice_slice = &a[1..4];
assert_eq!([2, 3, 4], nice_slice)
}