diff options
Diffstat (limited to 'info.toml')
| -rw-r--r-- | info.toml | 324 |
1 files changed, 323 insertions, 1 deletions
@@ -4,21 +4,42 @@ name = "variables1" path = "exercises/variables/variables1.rs" mode = "compile" +hint = """ +Hint: The declaration on line 5 is missing a keyword that is needed in Rust +to create a new variable binding.""" [[exercises]] name = "variables2" path = "exercises/variables/variables2.rs" mode = "compile" +hint = """ +The compiler message is saying that Rust cannot infer the type that the +variable binding `x` has with what is given here. +What happens if you annotate line 5 with a type annotation? +What if you give x a value? +What if you do both? +What type should x be, anyway? +What if x is the same type as 10? What if it's a different type?""" [[exercises]] name = "variables3" path = "exercises/variables/variables3.rs" mode = "compile" +hint = """ +In Rust, variable bindings are immutable by default. But here we're trying +to reassign a different value to x! There's a keyword we can use to make +a variable binding mutable instead.""" [[exercises]] name = "variables4" path = "exercises/variables/variables4.rs" mode = "compile" +hint = """ +Oops! In this exercise, we have a variable binding that we've created on +line 5, and we're trying to use it on line 6, but we haven't given it a +value. We can't print out something that isn't there; try giving x a value! +This is an error that can cause bugs that's very easy to make in any +programming language -- thankfully the Rust compiler has caught this for us!""" # IF @@ -26,6 +47,15 @@ mode = "compile" name = "if1" path = "exercises/if/if1.rs" mode = "test" +hint = """ +It's possible to do this in one line if you would like! +Some similar examples from other languages: +- In C(++) this would be: `a > b ? a : b` +- In Python this would be: `a if a > b else b` +Remember in Rust that: +- the `if` condition does not need to be surrounded by parentheses +- `if`/`else` conditionals are expressions +- Each condition is followed by a `{}` block.""" # FUNCTIONS @@ -33,26 +63,50 @@ mode = "test" name = "functions1" path = "exercises/functions/functions1.rs" mode = "compile" +hint = """ +This main function is calling a function that it expects to exist, but the +function doesn't exist. It expects this function to have the name `call_me`. +It expects this function to not take any arguments and not return a value. +Sounds a lot like `main`, doesn't it?""" [[exercises]] name = "functions2" path = "exercises/functions/functions2.rs" mode = "compile" +hint = """ +Rust requires that all parts of a function's signature have type annotations, +but `call_me` is missing the type annotation of `num`.""" [[exercises]] name = "functions3" path = "exercises/functions/functions3.rs" mode = "compile" +hint = """ +This time, the function *declaration* is okay, but there's something wrong +with the place where we're calling the function.""" [[exercises]] name = "functions4" path = "exercises/functions/functions4.rs" mode = "compile" +hint = """ +The error message points to line 12 and says it expects a type after the +`->`. This is where the function's return type should be-- take a look at +the `is_even` function for an example!""" [[exercises]] name = "functions5" path = "exercises/functions/functions5.rs" mode = "compile" +hint = """ +This is a really common error that can be fixed by removing one character. +It happens because Rust distinguishes between expressions and statements: expressions return +a value based on its operand, and statements simply return a () type which behaves just like `void` in C/C++ language. +We want to return a value of `i32` type from the `square` function, but it is returning a `()` type... +They are not the same. There are two solutions: +1. Add a `return` ahead of `num * num;` +2. remove `;`, make it to be `num * num` +""" # TEST 1 @@ -60,6 +114,7 @@ mode = "compile" name = "test1" path = "exercises/test1.rs" mode = "test" +hint = "No hints this time ;)" # PRIMITIVE TYPES @@ -67,31 +122,64 @@ mode = "test" name = "primitive_types1" path = "exercises/primitive_types/primitive_types1.rs" mode = "compile" +hint = "No hints this time ;)" [[exercises]] name = "primitive_types2" path = "exercises/primitive_types/primitive_types2.rs" mode = "compile" +hint = "No hints this time ;)" [[exercises]] name = "primitive_types3" path = "exercises/primitive_types/primitive_types3.rs" mode = "compile" +hint = """ +There's a shorthand to initialize Arrays with a certain size that does not +require you to type in 100 items (but you certainly can if you want!). +For example, you can do: +let array = ["Are we there yet?"; 10]; + +Bonus: what are some other things you could have that would return true +for `a.len() >= 100`?""" [[exercises]] name = "primitive_types4" path = "exercises/primitive_types/primitive_types4.rs" mode = "test" +hint = """ +Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book: +https://doc.rust-lang.org/book/ch04-03-slices.html +and use the starting and ending indices of the items in the Array +that you want to end up in the slice. + +If you're curious why the right hand of the `==` comparison does not +have an ampersand for a reference since the left hand side is a +reference, take a look at the Deref coercions section of the book: +https://doc.rust-lang.org/book/ch15-02-deref.html +""" [[exercises]] name = "primitive_types5" path = "exercises/primitive_types/primitive_types5.rs" mode = "compile" +hint = """ +Take a look at the Data Types -> The Tuple Type section of the book: +https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type +Particularly the part about destructuring (second to last example in the section). +You'll need to make a pattern to bind `name` and `age` to the appropriate parts +of the tuple. You can do it!!""" [[exercises]] name = "primitive_types6" path = "exercises/primitive_types/primitive_types6.rs" mode = "compile" +hint = """ +While you could use a destructuring `let` for the tuple here, try +indexing into it instead, as explained in the last example of the +Data Types -> The Tuple Type section of the book: +https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type +Now you have another tool in your toolbox!""" # STRUCTS @@ -99,11 +187,13 @@ mode = "compile" name = "structs1" path = "exercises/structs/structs1.rs" mode = "test" +hint = "No hints this time ;)" [[exercises]] name = "structs2" path = "exercises/structs/structs2.rs" mode = "test" +hint = "No hints this time ;)" # STRINGS @@ -111,11 +201,22 @@ mode = "test" name = "strings1" path = "exercises/strings/strings1.rs" mode = "compile" +hint = """ +The `current_favorite_color` function is currently returning a string slice with the `'static` +lifetime. We know this because the data of the string lives in our code itself -- it doesn't +come from a file or user input or another program -- so it will live as long as our program +lives. But it is still a string slice. There's one way to create a `String` by converting a +string slice covered in the Strings chapter of the book, and another way that uses the `From` +trait.""" [[exercises]] name = "strings2" path = "exercises/strings/strings2.rs" mode = "compile" +hint = """ +Yes, it would be really easy to fix this by just changing the value bound to `word` to be a +string slice instead of a `String`, wouldn't it?? There is a way to add one character to line +6, though, that will coerce the `String` into a string slice.""" # TEST 2 @@ -123,6 +224,7 @@ mode = "compile" name = "test2" path = "exercises/test2.rs" mode = "compile" +hint = "No hints this time ;)" # ENUMS @@ -130,16 +232,22 @@ mode = "compile" name = "enums1" path = "exercises/enums/enums1.rs" mode = "compile" +hint = """ +Hint: The declaration of the enumeration type has not been defined yet.""" [[exercises]] name = "enums2" path = "exercises/enums/enums2.rs" mode = "compile" +hint = """ +Hint: you can create enumerations that have different variants with different types +such as no data, anonymous structs, a single string, tuples, ...etc""" [[exercises]] name = "enums3" path = "exercises/enums/enums3.rs" mode = "test" +hint = "No hints this time ;)" # TESTS @@ -147,16 +255,31 @@ mode = "test" name = "tests1" path = "exercises/tests/tests1.rs" mode = "test" +hint = """ +You don't even need to write any code to test -- you can just test values and run that, even +though you wouldn't do that in real life :) `assert!` is a macro that needs an argument. +Depending on the value of the argument, `assert!` will do nothing (in which case the test will +pass) or `assert!` will panic (in which case the test will fail). So try giving different values +to `assert!` and see which ones compile, which ones pass, and which ones fail :)""" [[exercises]] name = "tests2" path = "exercises/tests/tests2.rs" mode = "test" +hint = """ +Like the previous exercise, you don't need to write any code to get this test to compile and +run. `assert_eq!` is a macro that takes two arguments and compares them. Try giving it two +values that are equal! Try giving it two arguments that are different! Try giving it two values +that are of different types! Try switching which argument comes first and which comes second!""" [[exercises]] name = "tests3" path = "exercises/tests/tests3.rs" mode = "test" +hint = """ +You can call a function right where you're passing arguments to `assert!` -- so you could do +something like `assert!(having_fun())`. If you want to check that you indeed get false, you +can negate the result of what you're doing using `!`, like `assert!(!having_fun())`.""" # TEST 3 @@ -164,6 +287,7 @@ mode = "test" name = "test3" path = "exercises/test3.rs" mode = "test" +hint = "No hints this time ;)" # MODULES @@ -171,11 +295,21 @@ mode = "test" name = "modules1" path = "exercises/modules/modules1.rs" mode = "compile" +hint = """ +Everything is private in Rust by default-- but there's a keyword we can use +to make something public! The compiler error should point to the thing that +needs to be public.""" [[exercises]] name = "modules2" path = "exercises/modules/modules2.rs" mode = "compile" +hint = """ +The delicious_snacks module is trying to present an external +interface (the `fruit` and `veggie` constants) that is different than +its internal structure (the `fruits` and `veggies` modules and +associated constants). It's almost there except for one keyword missing for +each constant.""" # MACROS @@ -183,28 +317,48 @@ mode = "compile" name = "macros1" path = "exercises/macros/macros1.rs" mode = "compile" +hint = """ +When you call a macro, you need to add something special compared to a +regular function call. If you're stuck, take a look at what's inside +`my_macro`.""" [[exercises]] name = "macros2" path = "exercises/macros/macros2.rs" mode = "compile" +hint = """ +Macros don't quite play by the same rules as the rest of Rust, in terms of +what's available where. + +Unlike other things in Rust, the order of "where you define a macro" versus +"where you use it" actually matters.""" [[exercises]] name = "macros3" path = "exercises/macros/macros3.rs" mode = "compile" +hint = """ +In order to use a macro outside of its module, you need to do something +special to the module to lift the macro out into its parent. + +The same trick also works on "extern crate" statements for crates that have +exported macros, if you've seen any of those around.""" [[exercises]] name = "macros4" path = "exercises/macros/macros4.rs" mode = "compile" - +hint = """ +You only need to add a single character to make this compile. +The way macros are written, it wants to see something between each +"macro arm", so it can separate them.""" # TEST 4 [[exercises]] name = "test4" path = "exercises/test4.rs" mode = "compile" +hint = "No hints this time ;)" # MOVE SEMANTICS @@ -212,21 +366,55 @@ mode = "compile" name = "move_semantics1" path = "exercises/move_semantics/move_semantics1.rs" mode = "compile" +hint = """ +So you've got the "cannot borrow immutable local variable `vec1` as mutable" error on line 11, +right? The fix for this is going to be adding one keyword, and the addition is NOT on line 11 +where the error is.""" [[exercises]] name = "move_semantics2" path = "exercises/move_semantics/move_semantics2.rs" mode = "compile" +hint = """ +So `vec0` is being *moved* into the function `fill_vec` when we call it on +line 7, which means it gets dropped at the end of `fill_vec`, which means we +can't use `vec0` again on line 10 (or anywhere else in `main` after the +`fill_vec` call for that matter). We could fix this in a few ways, try them +all! +1. Make another, separate version of the data that's in `vec0` and pass that + to `fill_vec` instead. +2. Make `fill_vec` borrow its argument instead of taking ownership of it, + and then copy the data within the function in order to return an owned + `Vec<i32>` +3. Make `fill_vec` *mutably* borrow its argument (which will need to be + mutable), modify it directly, then not return anything. Then you can get rid + of `vec1` entirely -- note that this will change what gets printed by the + first `println!`""" [[exercises]] name = "move_semantics3" path = "exercises/move_semantics/move_semantics3.rs" mode = "compile" +hint = """ +The difference between this one and the previous ones is that the first line +of `fn fill_vec` that had `let mut vec = vec;` is no longer there. You can, +instead of adding that line back, add `mut` in one place that will change +an existing binding to be a mutable binding instead of an immutable one :)""" [[exercises]] name = "move_semantics4" path = "exercises/move_semantics/move_semantics4.rs" mode = "compile" +hint = """ +Stop reading whenever you feel like you have enough direction :) Or try +doing one step and then fixing the compiler errors that result! +So the end goal is to: + - get rid of the first line in main that creates the new vector + - so then `vec0` doesn't exist, so we can't pass it to `fill_vec` + - we don't want to pass anything to `fill_vec`, so its signature should + reflect that it does not take any arguments + - since we're not creating a new vec in `main` anymore, we need to create + a new vec in `fill_vec`, similarly to the way we did in `main`""" # ERROR HANDLING @@ -234,21 +422,78 @@ mode = "compile" name = "errors1" path = "exercises/error_handling/errors1.rs" mode = "test" +hint = """ +`Err` is one of the variants of `Result`, so what the 2nd test is saying +is that `generate_nametag_text` should return a `Result` instead of an +`Option`. + +To make this change, you'll need to: + - update the return type in the function signature to be a Result<String, String> that + could be the variants `Ok(String)` and `Err(String)` + - change the body of the function to return `Ok(stuff)` where it currently + returns `Some(stuff)` + - change the body of the function to return `Err(error message)` where it + currently returns `None` + - change the first test to expect `Ok(stuff)` where it currently expects + `Some(stuff)`.""" [[exercises]] name = "errors2" path = "exercises/error_handling/errors2.rs" mode = "test" +hint = """ +One way to handle this is using a `match` statement on +`item_quantity.parse::<i32>()` where the cases are `Ok(something)` and +`Err(something)`. This pattern is very common in Rust, though, so there's +a `?` operator that does pretty much what you would make that match statement +do for you! Take a look at this section of the Error Handling chapter: +https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator +and give it a try!""" [[exercises]] name = "errors3" path = "exercises/error_handling/errors3.rs" mode = "test" +hint = """ +If other functions can return a `Result`, why shouldn't `main`?""" [[exercises]] name = "errors4" path = "exercises/error_handling/errorsn.rs" mode = "test" +hint = """ +First hint: To figure out what type should go where the ??? is, take a look +at the test helper function `test_with_str`, since it returns whatever +`read_and_validate` returns and`test_with_str` has its signature fully +specified. + + +Next hint: There are three places in `read_and_validate` that we call a +function that returns a `Result` (that is, the functions might fail). +Apply the `?` operator on those calls so that we return immediately from +`read_and_validate` if those function calls fail. + + +Another hint: under the hood, the `?` operator calls `From::from` +on the error value to convert it to a boxed trait object, a Box<dyn error::Error>, +which is polymorphic-- that means that lots of different kinds of errors +can be returned from the same function because all errors act the same +since they all implement the `error::Error` trait. +Check out this section of the book: +https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator + + +Another another hint: Note that because the `?` operator returns +the *unwrapped* value in the `Ok` case, if we want to return a `Result` from +`read_and_validate` for *its* success case, we'll have to rewrap a value +that we got from the return value of a `?`ed call in an `Ok`-- this will +look like `Ok(something)`. + + +Another another another hint: `Result`s must be "used", that is, you'll +get a warning if you don't handle a `Result` that you get in your +function. Read more about that in the `std::result` module docs: +https://doc.rust-lang.org/std/result/#results-must-be-used""" # OPTIONS / RESULTS @@ -256,11 +501,21 @@ mode = "test" name = "option1" path = "exercises/error_handling/option1.rs" mode = "test" +hint = """ +Try using a `match` statement where the arms are `Some(thing)` and `None`. +Or set a default value to print out if you get `None` by using the +function `unwrap_or`. +Or use an `if let` statement on the result of `pop()` to both destructure +a `Some` value and only print out something if we have a value!""" [[exercises]] name = "option2" path = "exercises/error_handling/result1.rs" mode = "test" +hint = """ +`PositiveNonzeroInteger::new` is always creating a new instance and returning an `Ok` result. +It should be doing some checking, returning an `Err` result if those checks fail, and only +returning an `Ok` result if those checks determine that everything is... okay :)""" # STANDARD LIBRARY TYPES @@ -268,21 +523,56 @@ mode = "test" name = "arc1" path = "exercises/standard_library_types/arc1.rs" mode = "compile" +hint = """ +Make `shared_numbers` be an `Arc` from the numbers vector. Then, in order +to avoid creating a copy of `numbers`, you'll need to create `child_numbers` +inside the loop but still in the main thread. + +`child_numbers` should be a clone of the Arc of the numbers instead of a +thread-local copy of the numbers.""" [[exercises]] name = "iterators2" path = "exercises/standard_library_types/iterators2.rs" mode = "test" +hint = """ +Step 1 +You need to call something on `first` before it can be collected +Currently its type is `char`. Have a look at the methods that are available on that type: +https://doc.rust-lang.org/std/primitive.char.html + + +Step 2 +First you'll need to turn the Vec into an iterator +Then you'll need to apply your function unto each item in the vector +P.s. Don't forget to collect() at the end! + + +Step 3. +This is very similar to the previous test. The only real change is that you will need to +alter the type that collect is coerced into. For a bonus you could try doing this with a +turbofish""" [[exercises]] name = "iterators3" path = "exercises/standard_library_types/iterators3.rs" mode = "test" +hint = """ +Minor hint: In each of the two cases in the match in main, you can create x with either +a 'turbofish' or by hinting the type of x to the compiler. You may try both. + +Major hint: Have a look at the Iter trait and at the explanation of its collect function. +Especially the part about Result is interesting.""" [[exercises]] name = "iterators4" path = "exercises/standard_library_types/iterators4.rs" mode = "test" +hint = """ +In an imperative language you might write a for loop to iterate through +multiply the values into a mutable variable. Or you might write code more +functionally with recursion and a match clause. But you can also use ranges +and iterators to solve this in rust.""" # THREADS @@ -290,3 +580,35 @@ mode = "test" name = "threads1" path = "exercises/threads/threads1.rs" mode = "compile" +hint = """ +`Arc` is an Atomic Reference Counted pointer that allows safe, shared access +to **immutable** data. But we want to *change* the number of `jobs_completed` +so we'll need to also use another type that will only allow one thread to +mutate the data at a time. Take a look at this section of the book: +https://doc.rust-lang.org/book/ch16-03-shared-state.html#atomic-reference-counting-with-arct +and keep reading if you'd like more hints :) + + +Do you now have an `Arc` `Mutex` `JobStatus` at the beginning of main? Like: +`let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));` +Similar to the code in the example in the book that happens after the text +that says "We can use Arc<T> to fix this.". If not, give that a try! If you +do and would like more hints, keep reading!! + + +Make sure neither of your threads are holding onto the lock of the mutex +while they are sleeping, since this will prevent the other thread from +being allowed to get the lock. Locks are automatically released when +they go out of scope. + +Ok, so, real talk, this was actually tricky for *me* to do too. And +I could see a lot of different problems you might run into, so at this +point I'm not sure which one you've hit :) + +Please open an issue if you're still running into a problem that +these hints are not helping you with, or if you've looked at the sample +answers and don't understand why they work and yours doesn't. + +If you've learned from the sample solutions, I encourage you to come +back to this exercise and try it again in a few days to reinforce +what you've learned :)""" |