diff options
Diffstat (limited to 'info.toml')
| -rw-r--r-- | info.toml | 157 |
1 files changed, 79 insertions, 78 deletions
@@ -260,8 +260,8 @@ name = "vecs2" path = "exercises/vecs/vecs2.rs" mode = "test" hint = """ -Hint 1: `i` is each element from the Vec as they are being iterated. Can you try -multiplying this? +Hint 1: `element` is each element from the Vec as they are being iterated. Can you +try multiplying this? Hint 2: For the first function, there's a way to directly access the numbers stored in the Vec, using the * dereference operator. You can both access and write to the @@ -287,23 +287,24 @@ Also: Try accessing `vec0` after having called `fill_vec()`. See what happens!"" [[exercises]] name = "move_semantics2" path = "exercises/move_semantics/move_semantics2.rs" -mode = "compile" +mode = "test" hint = """ -So, `vec0` is passed into the `fill_vec` function as an argument. In Rust, -when an argument is passed to a function and it's not explicitly returned, -you can't use the original variable anymore. We call this "moving" a variable. -Variables that are moved into a function (or block scope) and aren't explicitly -returned get "dropped" at the end of that function. This is also what happens here. -There's a few ways to fix this, try them all if you want: -1. Make another, separate version of the data that's in `vec0` and pass that +When running this exercise for the first time, you'll notice an error about +"borrow of moved value". In Rust, when an argument is passed to a function and +it's not explicitly returned, you can't use the original variable anymore. +We call this "moving" a variable. When we pass `vec0` into `fill_vec`, it's being +"moved" into `vec1`, meaning we can't access `vec0` anymore after the fact. +Rust provides a couple of different ways to mitigate this issue, feel free to try them all: +1. You could 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 a reference to 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!`""" + and then copy the data within the function (`vec.clone()`) in order to return an owned + `Vec<i32>`. +3. Or, you could make `fill_vec` *mutably* borrow a reference to its argument (which will need to be + mutable), modify it directly, then not return anything. This means that `vec0` will change over the + course of the function, and makes `vec1` redundant (make sure to change the parameters of the `println!` + statements if you go this route) +""" [[exercises]] name = "move_semantics3" @@ -905,67 +906,6 @@ The fold method can be useful in the count_collection_iterator function. For a further challenge, consult the documentation for Iterator to find a different method that could make your code more compact than using fold.""" -# THREADS - -[[exercises]] -name = "threads1" -path = "exercises/threads/threads1.rs" -mode = "compile" -hint = """ -`JoinHandle` is a struct that is returned from a spawned thread: -https://doc.rust-lang.org/std/thread/fn.spawn.html - -A challenge with multi-threaded applications is that the main thread can -finish before the spawned threads are completed. -https://doc.rust-lang.org/book/ch16-01-threads.html#waiting-for-all-threads-to-finish-using-join-handles - -Use the JoinHandles to wait for each thread to finish and collect their results. -https://doc.rust-lang.org/std/thread/struct.JoinHandle.html -""" - -[[exercises]] -name = "threads2" -path = "exercises/threads/threads2.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. - -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 :)""" - -[[exercises]] -name = "threads3" -path = "exercises/threads/threads3.rs" -mode = "compile" -hint = """ -An alternate way to handle concurrency between threads is to use -a mpsc (multiple producer, single consumer) channel to communicate. -With both a sending end and a receiving end, it's possible to -send values in one thread and receive them in another. -Multiple producers are possible by using clone() to create a duplicate -of the original sending end. -See https://doc.rust-lang.org/book/ch16-02-message-passing.html for more info. -""" - # SMART POINTERS [[exercises]] @@ -1028,6 +968,67 @@ Check out https://doc.rust-lang.org/std/borrow/enum.Cow.html for documentation on the `Cow` type. """ +# THREADS + +[[exercises]] +name = "threads1" +path = "exercises/threads/threads1.rs" +mode = "compile" +hint = """ +`JoinHandle` is a struct that is returned from a spawned thread: +https://doc.rust-lang.org/std/thread/fn.spawn.html + +A challenge with multi-threaded applications is that the main thread can +finish before the spawned threads are completed. +https://doc.rust-lang.org/book/ch16-01-threads.html#waiting-for-all-threads-to-finish-using-join-handles + +Use the JoinHandles to wait for each thread to finish and collect their results. +https://doc.rust-lang.org/std/thread/struct.JoinHandle.html +""" + +[[exercises]] +name = "threads2" +path = "exercises/threads/threads2.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. + +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 :)""" + +[[exercises]] +name = "threads3" +path = "exercises/threads/threads3.rs" +mode = "compile" +hint = """ +An alternate way to handle concurrency between threads is to use +a mpsc (multiple producer, single consumer) channel to communicate. +With both a sending end and a receiving end, it's possible to +send values in one thread and receive them in another. +Multiple producers are possible by using clone() to create a duplicate +of the original sending end. +See https://doc.rust-lang.org/book/ch16-02-message-passing.html for more info. +""" + # MACROS [[exercises]] @@ -1170,4 +1171,4 @@ name = "as_ref_mut" path = "exercises/conversions/as_ref_mut.rs" mode = "test" hint = """ -Add AsRef<str> as a trait bound to the functions.""" +Add AsRef<str> or AsMut<u32> as a trait bound to the functions.""" |