What is elm

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Sign in. Will Elm ever be ready? Chris Gregori Follow. Collaborate to develop…. Inherit protocol and endpoint when not specified. Bits and Pieces Follow. Written by Chris Gregori Follow. More From Medium. Models, Objects, and Documents. Anthony Fields. How does an angular app work? Vivek Singh Bisht in Frontend Weekly. A Quick Overview. Dipesh Bhoir. Mahbub Zulkarnain. Minhajul Abedin Rahat. Portals and giant carousels. And thus get rid of all those usual undefined is not a function errors.

If there might be a failure then the type will explicitly convey this information and the compiler will force this case to be handled by the programmer. As Elm is a pure functional language, the purpose of evaluating something is to get a value from it. Thus, Elm forces the developer to provide a return value for every control statement.

This implies that every if statement needs an else clause and case statements must handle every possible input value. For example, let's take a look at an abstract data type TypingDiscipline that might assume as value Static ; Dynamic or Gradual :.

Thus when changing our types to add more functionality, we end up being notified by the compiler that there is some code needing to be added in order to deal with a new possibility. Elm's short feedback loop and uncluttered syntax make it a very pleasant environment to work with. Let's take a look at how these things contribute to the Elm's developer joy. Avoid success at all costs. Simon Peyton Jones , Major contributor to the design of the Haskell programming language. An interesting consequence of the previously described safety features is how they shorten the feedback loop.

The programming activity usually consists on iterating through the following activities:. The last step is often where the developers spend most time, and this time is either spent writing automated tests or interacting with the program to confirm that it is correct. Most programmers would say this phase to be the least joyful one.

Elm's safety and lack of runtime exceptions transfers part of the Testing phase effort into the Compiling phase. When using Elm, the programmer will spend a bit more time on the compiling phase - interacting with the compiler until the program is considered correct - and much less time in the testing phase, when the only thing that may fail is whether the business requirements are met - and not whether the program crashes or not.

When using Elm, the programmer will have feedback about his mistakes sooner, not having to spend so much time in the lengthy testing phase. Elm's syntax is inspired by Haskell and minimalist. There are only two control statements; and very few reserved words. The center of this syntax is the function. If the most used syntactic feature of any structured programming language is the function invocation, then why do most Algol-style languages resort to so many special characters for function invocation and definition?

In order to write the above definition and invocation, we had to type 8 special characters for the function definition:. Depending on your keyboard's language, the number of pressed modifier-keys; annoyance and premature repetitive-strain-injury will vary. Elm cleans this up. If the function is such an important thing it should be easily typed and edited:. As you see, this function definition doesn't need any special characters. Type signatures are optional and automatically inferred by the compiler, so that we can swiftly experiment without having to explicitly enter them.

Nonetheless, they are useful: sometimes it is handy to have the type signature as guidance while writing a less obvious piece of code, and they often are a useful form of documentation. Thus, in Elm, type signatures are optionally written in a separate line some editors will generate the type signature automatically when we ask for it! Another feature that makes the language rather fun to use is that every function is curried and may thus be applied to a subset of its arguments, returning a so called partially-applied function that awaits only the missing arguments.

Thus, the following code :. Though if we chain these operations we start to get a sea of nested parens typical from a Lisp :. They allow chaining function application with a syntax akin to threading an argument through a pipeline of transformations:. This conveniently succinct syntax, together with the nice error messages end up making Elm very fit for interactive experimentation, both by using the REPL and by using the compiler. This is one of the things Redux got from implementing the Elm architecture.

When developing and trying a program we are able to inspect the actions performed on that interface and to go back and forth in time in order to analyze the state of the program at each moment of its execution.

In Redux this functionality is rather fragile due to the imperative nature of Javascript, and in order to cope with it, one is required to use Immutable or another library to avoid directly mutating the state of the application.

In Elm, this problem simply does not exist, because there's no such thing as mutation at the language level. The language design itself protects us from this kind of problems and from the need of using additional libraries.

However, large programs written in it can be a nightmare to maintain. Programmers tend to write mountain of tests to prevent JavaScript programs from misbehaving in production. They also use elaborate architectural patterns to make adding new features to their apps less painful. What we need is a language that not only provides the robustness inherent in languages from the ML family, but also is highly usable like JavaScript.

Elm is one such language. Elm is a functional programming language for building front-end web applications. It brings the best of both worlds when it comes to building highly robust applications with ease.

Besides maintainability and usability, Elm provides a plethora of benefits that are not present in most mainstream languages such as immutable values, stateless functions, type inference, pattern matching, automatic code formatting, and a great debugger.

We will explore each of these concepts in detail in chapter 4. Finally, Elm provides a novel architecture for organizing code which makes managing data flow between various components a breeze.

We often have to compare and contrast multiple frameworks which is confusing and time consuming.