You have already seen one of the most important functions in the language: the main function, which is the entry point of many programs. In this Rust tutorial we learn how to create our own custom data types, with structs, that groups variables and functions together into reusable units and help us model our application like real world entities. Rust - Traits - GeeksforGeeks Start by creating a new binary package: $ cargo new --bin example Edit Cargo.toml to include the following dependencies: azure-functions = "0.2.6" log = "0.4.2" Azure Functions are implemented by applying a #[func] attribute to a Rust function. In the following example, because take (5) was added after filter (), it will stop filtering after the fifth successful filter. Call Javascript from Rust - Rust By Example -- Extended ... Moreover, with time, life brings us to different paths and interests, so time is what it is, and we do have not the "fortune" to stay in . Error Handling - The Rust Programming Language No None or Some at sight. This syntax for new() looks a little different. However it is often desired that the callback is targeted to a special Rust object. Rust does not have constructors as a language construct. Example 2: AI inference. Rust Array | How Array works in Rust with Examples? Functions organize the program into logical blocks of code. The let keyword can't be used in the global scope. Since get_current_date doesn't have context of what to do when they return errors, it uses pattern matching to propagate the errors to main . You've also seen the "fn" keyword, which allows you to declare new functions. Note that in my example, the closure is invisible to the user, you could return a Fn(u64) -> u64 instead but them you expose the implementation of UnOp, your choice. Once defined, functions may be called to access code. Rust requires that all types in function signatures are specified. Split. Every now and then when using native libraries from Rust you'll be asked to pass a callback across the FFI boundary. This is similar to Java 8 Optional or Haskell's Maybe. The returned token . Calling a Rust function from C++. Instead, we can represent a value that might or might not exist with the Option type. OK, let's move on to an example. The rand crate is a very popular library in Rust to generate random numbers. Hello! Idiomatic approach for recursively applying a function. Example Suppose we wanted to write a function that shifts the given coordinates along the x-axis twice in the given . This is invalid syntax for Rust. We have assigned them different values to see the output. I'm working on a program that creates an initial GameState and repeatedly calls step () on it. One way to achieve this for functions that return Futures is to specify the full return type in the function signature. It's the most popular pattern in Rust for optional parameters. In handler.go, add the following code and save the file.This is your Go custom handler. . for an example invocation foo! The Rust standard library makes converting strings to integers dead simple. The map function here wraps the value returned by the extension function inside an Option<_> and since the extension function itself returns an Option<&str> the expression file_name . The return result for a function must define the type. It's also been voted the most loved programming language on StackOverflow's developer survey each year since 2016. This is a detailed example of exposing Rust code to other languages (in this case, Python). The nodejs-helper crate enables Rust functions to call Javascript functions in Node.js.. To see the complete source code and run it in Node.js, checkout here. The call rust.hello_world() will call a generated wrapper function, which in turn calls the Rust function hello_world defined in lib.rs. Examples of passing strings, structs, and callback functions between Java and Rust Getting Started The best place to start looking at the examples is in the test code ( GreetingsTest.java ). (bar) the input token stream would consist of the bar token. One way to achieve this for functions that return Futures is to specify the full return type in the function signature. It . Newtypes are very common in Rust code. Rust: Using Options by example. The cornerstone of abstraction in Rust is traits: Traits are Rust's sole notion of interface. Unlike how futures are implemented in other languages, a Rust future does not represent a computation happening in the background, rather the Rust future is the computation itself. fn main() { add(2, 3); } fn add(x: i32, y: i32) { let sum = x + y; println! A trait can be implemented by multiple types, and in fact new traits can provide implementations for existing types. Pointers, as the joke goes, are very pointy: it's easy to accidentally stab yourself. Think of it this way: Rust is a language that emphasizes safety. Rust requires that all types in function signatures are specified. For example, if our function adds two integer numbers together and returns an integer result, we can choose i32 as the function type. So, we have to make compiler to follow C's name mangling with no_mangling attribute. Random numbers. Here, the function type A -> B is taken to be any type that implements a corresponding Fn* trait, for example Fn(A) -> B, FnMut(A) -> B and FnOnce(A) -> B. A common example, used in this post, are shapes. The actions folder contains zipped, precompiled actions that you can use to deploy "native" actions in IBM Cloud Functions (if you don't want to compile the Rust code from scratch).. Since its first open-source release in 2015, the Rust programming language has gained a lot of attention from the community. Only static gives us a . Targeting callbacks to Rust objects. The result is the same. In Rust, the async keyword creates a Future whereas the .await keyword destroys it. This makes the code reusable. The codes also use thee elapsed() function on an Instant object to get a Duration object. However, specifying the exact type can be verbose, brittle, and difficult. To write a procedural macro, we need to write our parser to parse TokenStream. You've also seen the fn keyword, which allows you to declare new functions.. Rust code uses snake case as the conventional style for function and variable names. Functions that perform asynchronous operations are labeled with the async keyword. In this example, we are trying to create the usize type variable in the rust and trying to print it using the println! The second demo application allows users to upload an image and then invoke a serverless function to classify the main subject on the image. An example where the Option is used inside Rust is the pop method for vectors. The implementation of each function is contained in the /src/fetch_all.rs and /src . One way to achieve this for functions that return Future s is to specify the full return type in the function signature. In this Rust tutorial we learn how to create our own custom data types, with structs, that groups variables and functions together into reusable units and help us model our application like real world entities. Specifically, Rust is a "type safe language", meaning that the compiler ensures that every program has well-defined behavior.Although other languages make the same guarantee, Rust does so without a garbage collector, runtime, or manual . Rust achieves memory safety without garbage collection, and reference counting is optional. Functions are the building blocks of readable, maintainable, and reusable code. And we have to sync ABI with extern "C".. Like this, Rust's module system is surprisingly confusing and causes a lot of frustration for beginners. "My co-worker wrote a function that looks like this: fn succ(x: &int) -> int { *x + 1 } Async functions in Rust Async functions in Rust differ somewhat from what you're used to. Basic Function. In snake case, all letters are lowercase and . The way unsafe works is like this: you use it by declaring that you'd like to enter the unsafe boundary by applying the unsafe keyword to either a function or a block. Rust is a safe systems programming language. It would be nice to be able to define a function like this: Rust has been called a systems programming language and . It is a function that takes no arguments (hence the empty parentheses) and returns a unit, also written (). Downsides. Parsing integers. Save it as handler.go in the function app root (in the same folder as host.json).. . The minimality of TokenTree is crucial, however, for stabilization. Rust cannot tell that a method only accesses one field, so the fields should be structs with their own methods for implementation convenience. In your project's Cargo.toml, add dependency for the nodejs-helper and wasm-bindgen crates. The Cargo.toml file contains configuration (packages and metadata) for the two Rust programs that are used in this tutorial. Our C++ blobstore supports a put operation for a discontiguous buffer upload. Each call to step () will return either a new GameState, or a Score value. In this post, I'll explain the module system using practical examples so you get a clear understanding of how it works and can immediately start applying this in your projects. Although C and C++ are systems languages, they're not safe. Rust is syntactically similar to C++, but can guarantee memory safety by using a borrow checker to validate references. - A function can be considered as a higher-order function only if it takes one or more functions as parameters or if it returns another function as a result. NOTE: In this example, we are using the exported function from the wasm module directly to help highlight the WebAssembly API. Rust is a multi-paradigm, general-purpose programming language designed for performance and safety, especially safe concurrency. Because Rust uses a lazy model of functional programming, like Haskell, it only computes what it needs. This is a sample example for beginners to understand how usize type work and implement it in rust. Main function. If the function is non-void and if the output it returns can be empty, If the value, of a property of the data type can be empty, We have to use their data type as an Option type; For example, if the function outputs a &str value and the output can be empty, the return type of the function should set as Option<&str>. The File struct represents a file. If the result is a Score, it should be returned, but if it's GameState, step () should be called again. Each shape can be considered it's own type, however, will implement many of the same functions as other shapes. Functions are prevalent in Rust code. For example, the entirety of the Rust compiler 1 and all of the Rust standard library are written in Rust (with the help of some carefully encapsulated unsafe code). . Go; Rust; Press Ctrl + N (Cmd + N on macOS) to create a new file. The struct can still be reused in different calls. There are two function calls inside the get_current_date function (get and json) that return Result values. Let's start off creating an example function that returns a Result. A pointer to a function always implements all three of these, but Rust also has closures, that may or may not be converted to pointers (depending on whether the capture set is empty) to functions but they do implement some of these traits. Rust Functions Tutorial. For example (a, b) is a Group with parentheses as delimiters, and the internal token stream is a, b. Example: Rust was designed by Mozilla and is considered a system programming language (like wasm-bindgen generates JavaScript bindings code that can be imported as an ES6 import, and is the reccomended way to work with your Rust Wasm modules. To specify a data type, we write a -> operator followed by the type, after the parameter list parentheses. It would be nice to be able to define a function like this: But over time Rust's ambitions have gotten ever lower-level, and zero-cost abstraction is now a core principle. Then, in the second part, we will demonstrate two serverless function examples, both written in Rust and compiled to WebAssembly for deployment. ("Hello, world!"); } It only contains a main function—this is where the execution of the program begins. The way name mangling is different for each language (c++, rust).. Functions in Rust. Most of the questions around ownership come up when writing functions. Compiler do name mangling to reslove unique name of symbol. When you learned Rust, you probably noticed how it's very precise about what types the argument of a function has and what type the function returns. The first example showcases WasmEdge's fast image processing capabilities, whereas the second one runs AI inference powered by WasmEdge's TensorFlow extension . It makes you write down the types of the parameters and return values of functions, but within function bodies it can infer the type of most things so you don't need to . Rust requires that all types in function signatures are specified. Functions. synprovides a ready-made parser for Rust syntax that can be used to parse TokenStream. Deploy the repo to Vercel and you now have a Vercel Jamstack app with a high-performance Rust and WebAssembly based serverless backend. This is a guide to Rust Array. The Nomicon book - entire book dedicated to unsafe programming in Rust. Even the better ones out there typically don't have a pre-existing, reasonably complex program to work with. Then they use the as_millis() function on the Duration object to get the number of milliseconds from the time Instant::now() was used. Example of Rust usize. A trait object is always passed by a pointer and has a vtable so that methods can be dispatched dynamically. package main import ( "fmt" "log" "net/http" "os" ) func helloHandler(w http.ResponseWriter, r *http.Request) { message := "This HTTP triggered function . Running npm run serve should now compile everything and . It will only perform the minimal amount of calculations needed to obtain the results required. It allows a program to perform read-write operations on a file. Example: fn main() For example, I have been doing .NET moving to NodeJS/TypeScript with the serverless movement back in 2015 when the AWS Lambda function was generally available.. In Rust, you quickly learn that vector and slice types are not iterable themselves. Rust Structs (Structures) Tutorial. For those unfamiliar with the term, polymorphism is providing a single interface (group of functions) for multiple different types. Call Javascript from Rust. ("{} + {} = {}", x, y, sum); } Function with Return Value. In Rust, generic return values are a good example of this. If our model of the types in Rust includes const generic functions, this function can be explicitly described as a Rust function; otherwise it simply lives in our metatheory. Rust Structs (Structures) Tutorial. Rust Ownership by Example Updated 2021-05-01T15:50:00Z. Optional parameters are now associated to their name, which makes it easier to read. Downsides. Rust avoids the billion dollar mistake of including nulls in the language. 1. ↩. Oct 23, 2017. Most articles I've seen that cover this topic uses really trivial example functions, skipping over a lot of the complexity. LibC - a crate, that allows to call C function from Rust. Procedural macros are public functions that take TokenStream as input and return another TokenStream. Decreasing latency via buffering. In the example function, we check whether a string contains a minimum number of characters. For example, let's create src/greet.rs that implements a HTTP triggered function: The reasons are varied, but often this might be done to notify the caller when "interesting" things happen, for injecting logic (see the Strategy Pattern), or to handle the result of an asynchronous operation. However, specifying the exact type can be verbose, brittle, and difficult. However, specifying the exact type can be verbose, brittle, and difficult. VTable is a kind of function pointer array that contains the addresses of all virtual functions of this class. Example of call to the repository insert function. Somewhat verbose. Abstraction or representing units are the most common uses, but they can be used for other reasons: restricting functionality (reduce the functions exposed or traits implemented), making a type with copy semantics have move semantics, abstraction by providing a more concrete type and thus hiding internal . So for example, the example from above can be expanded: No None or Some at sight. Instead, the convention is to use an associated function new to create an object: #! It's so easy in fact, that it is . Therefore, Rust is made in a way such that you don't need them very often. A function is a set of statements to perform a specific task. Let's look again at our first project source code: fn main () { println! Recommended Articles. Calling libc function from nightly rust Example The libc crate is ' feature gated ' and can only be accessed on nightly Rust versions until it is considered stable. We can only use static or const.The latter declares a true constant, not a variable. Rust - File Input/ Output. Optional parameters are now associated to their name, which makes it easier to read. In our example it can be difficult to scale, since it needs a struct and a function per . In this article, different aspects such as introduction, syntax, working, and examples of Rust array are explained in detail. Depending on which tutorial or example you see first, you call .iter() or .into_iter(). Introduction. See the standard library documentation for more details. Moreover, functions make it easy to read . A trait object in Rust is similar to an object in Java or C++. A trait in Rust defines an interface. A set of examples using functions in Rust. I copied the example in actix-web welcome web page and changed it as below: use actix_web::{get, App, HttpRequest, HttpServer, Responder}; use std. So we aren't side-stepping the . The result is the same. Rust has a set of rules that allows one type to be coerced to another one. Many of us most likely professionally work with other languages. Example. Functions are the block of reusable code that can perform similar related actions. The function is the following: Let us take a journey through the world of iterators and figure . ↩ Let's expose very simple function. Rust split ExamplesSeparate strings with the split method, using a function to test for delimiter chars. It's the most popular pattern in Rust for optional parameters. In addition to reading and writing to console, Rust allows reading and writing to files. The Rust community has a very good crate, syn, for parsing TokenStream. You've already seen one of the most important functions in the language: the main function, which is the entry point of many programs. Please don't pay attention to the mess, it's under construction and it . Somewhat verbose. A simple skeleton of a function-like procedural macro looks like the following: As one can see this is in fact just a mapping from one TokenStream to another where the input will be the tokens inside of the invocation delimiters, e.g. Rust By Example Functions Its arguments are type annotated, just like variables, and, if the function returns a value, the return type must be specified after an arrow -> . If this were normal Rust, we'd just accept a closure (e.g. The former example showed how a global function can be called from C code. Rust program that takes substrings with slices Rust is the most-loved language. A lot of applications require random numbers. Rust uses the Hindley-Milner type system most commonly associated with ML-family languages, most famously Haskell. How about the other way around? In the previous article, we discussed how to call Rust functions from Javascript. Array in Rust is created using the [] square brackets and the size of array should be known during the compile time. Async functions differ in one important way: all your return types are "wrapped" into a Future. It supports a wide variety of random number generators and distributions, each with a different performance and security trade off. While this is conceptually simple, this may sound like there's not much we can do with this! (The external interface of the struct can be anything you like using suitable traits.) The body of the function, between curly . This method returns an Option<T>. Here goes the link to the GitHub repository with the complete code. We cover how to define and initialize a struct with values, access and mutate its properties and . In this example Rust's main() will call trigger_callback() in C, which would, in turn, call back to callback() in Rust. When processing text, we often need to separate apart the values in the strings. method of rust. I try write my first rust web demo with actix-web. Therefore, they cancel each other and async { foo.await } is equivalent to foo. When you specify the types of a function's arguments, you may choose how that value is passed in. a . We cover how to define and initialize a struct with values, access and mutate its properties and . We are using Generics and Traits to tell Rust that some type S must implement the trait Into for type String.The String type implements Into<String> as noop because we already have a String.The &str type implements Into<String> by using the same .to_string() method we were originally doing in the new() function. . Rust implements asynchronous programing using a feature called async/await. As a reminder, the function that we implemented in the previous section generates a stream of requests, but they are run sequentially. In Rust, this is quite easy to do with closures, it might look a bit verbose but if you are familiar with Rust then you should be fine. Rust queries related to "array as a parameter rust" rust pass array to function; function array argument rust; rust pass array element by reference; rust array as function parameter; how to pass any array in rust function; array type rust; rust array as argument; rust string function argument array number; rust pass array as type; rust . Hello world. In our example it can be difficult to scale, since it needs a struct and a function per . In our example, the connect function is defined like this: If you only need read-only access, you can take an immutable reference: The input parameters for a function must define the required incoming type. It's unclear, for example, how we might parse a function from a TokenStream. @MaiaVictor not really, a closure is just a function that can capture environment, you could do it by hand without problem it's would just be longer to write. If you do not realize both of these functions exist or that they do different things, you may find yourself fighting with the compiler to get your code to work. All methods in the File struct return a variant of the io::Result enumeration. The struct can still be reused in different calls. A concrete example of 'split borrrowing' will make this clearer. . Functions can be deployed using Netlify's CLI as well as the Netlify Build environment.. You can copy this repository and deploy it to Netlify by clicking the button below. Rust - Functions. Installation Hello World Cargo, Crates and Basic Project Structure Comments and Documenting the code Variable bindings, Constants and Statics Functions Primitive Data Types Operators Control FlowsBeyond The BasicsVectors Structs Enums Generics Impls and TraitsThe Tough PartOwnership Borrowing LifetimesLet's Get It StartedCode Organization . The following codes use Instant::now() to get the current time before each of our function runs. The Rust Book, Foreign Function Interface - section in the first edition for The Rust book, about how to do FFI. The Pin type is how Rust is able to support borrows in async functions. For example we might be uploading snapshots of a circular buffer which would tend to consist of 2 pieces, or fragments of a file spread across memory for some other reason (like a rope data structure). "But tutorial!" you may cry. Version 2 We access the same substring, but use the get() function and unwrap its result. Examples. You'll find here C type definitions, constants and standard functions. This example shows how to deploy Rust code on Netlify Functions. [allow(unused)] fn main() { /// Time in seconds. I'm going to start with trivial functions and build my way . Post, are shapes, rust function example & # x27 ; re not.. To upload an image and then invoke a serverless function to classify the main on. - functions not much we can represent a value that might or might not with... And it need them very often it allows a program to work other! We check whether a string contains a minimum number of characters s.! With Tokio and MongoDB | by Paolo Posso - Medium < /a > Calling a Rust function from Rust C!, that it is a function & # x27 ; s easy to accidentally stab yourself special Rust.. Rust achieves memory safety without garbage collection, and reusable code this class optional or Haskell & # ;. Goes, are very pointy: it & # x27 ; will make clearer... With the Async keyword the strings shows how to define and initialize a struct a... A way such that you don & # x27 ; m working on a File type and... Rust achieves memory safety without garbage collection, and reusable code to rust function example since. Systems languages, most famously Haskell and has a very good crate, that allows one type to be to. Struct return a variant of the bar token to reading and writing console. Blocks of code previous section generates a stream of requests, but can guarantee memory safety by using borrow. To Java 8 optional or Haskell & # x27 ; re not safe different performance and security trade....: //dfrasca.hashnode.dev/hello-serverless-rust '' > functions - Rust Design Patterns - GitHub Pages /a... This is a set of rules that allows one type to be coerced to another one a unit, written. Now compile everything and find here C type definitions, constants and standard functions type can verbose...: //www.tutorialspoint.com/rust/rust_functions.htm '' > unsafe in Rust - functions - the Rust and to! Construction and it also use thee elapsed ( ) on it variant of the can... Can still be reused in different calls a put operation for a function per functions may called... Array that contains the addresses of all virtual functions of this class and security trade off first, call... As a reminder, the function app root ( in the function signature an! Hence the empty parentheses ) and returns a Result initialize a struct with values access... Questions around ownership come up when writing functions your Go custom handler function from Rust,. Macro, we write a - & gt ; and Examples of Rust array are explained in.... Allows users to upload an image and then invoke a serverless function to the! Differ in one important way: all your return types are & quot wrapped! { println: //rust-unofficial.github.io/patterns/idioms/ctor.html '' > functions - Tutorialspoint < /a > Idiomatic for... Declares a true constant, not a variable Rust syntax that can difficult... Specific task to another one random numbers be called from C code a rust function example of... Second demo application allows users to upload an image and then invoke a serverless function classify! The codes also use thee elapsed ( ) function on an Instant object to get a object! Use an associated function new to create an object: # ( in this article, we need to a! ] fn main ( ) //www.tutorialspoint.com/rust/rust_functions.htm '' > Constructor - Rust Design Patterns - GitHub Pages /a. Async keyword systems programming language < /a > functions - IBM Developer < /a random. Choose how that value is passed in although C and C++ are systems languages most..., as the joke goes, are very pointy: it & # x27 s! Implementation of each function is a function: Rust < /a > Idiomatic approach for recursively a... Guarantee memory safety by using a borrow checker to validate references to see the Output how array works in -! Similar to C++, but can guarantee memory safety by using a borrow checker to validate.... A discontiguous buffer upload type system most commonly associated with ML-family languages, they cancel other! Cancel each other and Async { foo.await } is equivalent to foo - Tutorialspoint /a... Way to achieve this for functions that return Futures is rust function example use associated! Mangling to reslove unique name of symbol, it & # x27 ; s construction! Perform similar related actions achieves memory safety rust function example using a borrow checker to validate references Rust avoids the billion mistake... Represent a value that might or might not exist with the Option type generators and distributions, with... The Async keyword although C and rust function example are systems languages, they each!: //www.koderhq.com/tutorial/rust/struct/ '' > functions in Rust to generate random numbers or a Score value s unclear for. In seconds - a crate, syn, for stabilization billion dollar mistake of including in. This method returns an Option & lt ; t be used in this post, shapes. And security trade off, they cancel each other and Async { foo.await } is equivalent to.. Example for beginners to understand how usize type variable in the previous article, different such! Programming language < /a > functions - Tutorialspoint < /a > Hello.... As Introduction, syntax, working, and reusable code the building blocks of readable, maintainable, and fact! Functions differ in one important way: all your return types are quot. Or example you see first, you may choose how that value is passed in while this is conceptually,! Trade off wasm-bindgen crates recursively applying a function from C++ that return Futures to! - functions amount of calculations needed to obtain rust function example results required operation for a function: Rust /a! Let keyword can & # x27 ; t & gt ; operator followed by the type after! Each other and Async { foo.await } is equivalent to foo perform the minimal amount of calculations to. That value is passed in again at our first project source code fn. The better ones out there typically don & # x27 ; s under construction it... Another one for example, we discussed how to define and initialize a struct a. Similar rust function example actions or const.The latter declares a true constant, not a variable C++ Rust. All methods in the same folder as host.json ) or a Score value rand crate is a of. For recursively applying a function per is contained in the strings calls step ( ) each language C++., specifying the exact type can be dispatched dynamically brittle, and.... Easy in fact, that it is construction and it are now associated to their name, makes. Us take a journey through the world of iterators and figure parser to parse TokenStream ones out there don... To use an associated function new to create the usize type work implement! Invoke a serverless function to classify the main subject on the image:Result enumeration is always passed by a and. Code and save the file.This is your Go custom handler however, for parsing TokenStream, which makes easier... And implement it in Rust Rust code on Netlify functions t need them very often file.This your... Be verbose, brittle, and reference counting is optional is equivalent to foo to with. Passed in a discontiguous buffer upload see first, you may choose how that is! Mess, it & # x27 ; t need them very often you may choose how that is. That it is often desired that the callback is targeted to a Rust. Calculations needed to obtain the results required struct can be difficult to scale, it... The strings to classify the main subject on the image, constants and standard functions a,... It easier to read, all letters are lowercase and wide variety of random number generators and distributions each! The link to the GitHub repository with the Async keyword > Hello world book - entire book to! Requests, but can guarantee memory safety by using a borrow checker to references. A variant of the io::Result enumeration type, after the parameter list parentheses procedural. One important way: all your return types are & quot ; wrapped & quot ; wrapped & ;. Empty parentheses ) and returns a Result Nomicon book - entire book dedicated to unsafe programming in Rust Syntactic... Build my way they cancel each other and Async { foo.await } is equivalent to.. As the joke goes, are shapes specify a data type, we are trying to it... Main function questions around ownership come up when writing functions - functions - IBM Developer < >. Mangling with no_mangling attribute not safe previous section generates a stream of requests, but they are run sequentially apart. When writing functions parsing TokenStream this article, different aspects such as Introduction, syntax, working, and.! Whether a string contains a minimum number of characters the let keyword can & # x27 s. Function that we implemented in the function signature has been called a systems language! The input parameters for a function from Rust: //www.geeksforgeeks.org/functions-in-rust/ '' > -! The world of iterators and figure C & # x27 ; t be used in the same as! To parse TokenStream m going to start with trivial functions and build my way might parse a function must the. But they are run sequentially it needs a struct with values, access and its! Of rules that allows one type to be coerced to another one subject... Our example it can be verbose, brittle, and difficult ( packages and ).