When comparing Smalltalk vs Elm, the Slant community recommends Elm for most people. In the question“What is the best programming language to learn first?” Elm is ranked 13th while Smalltalk is ranked 15th. The most important reason people chose Elm is:
Lack of run-time exceptions makes it easy to produce large swathes of reliable front-end code without drowning in tests.
Specs
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Pros
Pro Environment of live objects
You can modify the system as it's running. You're "swimming with the fish", instead of probing a black box by remote control.
Pro Easy to learn and experiment
Pro Inspector makes objects transparent
Programmers must make detailed mental models of the system they are developing. Bugs usually happen when the mental model does not match the actual system. This is one of the greatest difficulties beginners have because most systems are so opaque. It takes a lot of effort to see what's really going on. But in Smalltalk this is much easier, thanks to the powerful tools included in the environment, like the object inspector.
Pro Superb Integrated Development Environment (IDE)
All tools (Inspector, Browser, Debugger etc.) are written in Smalltalk and are live objects in the environment. All sources are present, so that the tools can easily be studied, changed and experimented with.
The same goes for the other components like the compiler, OS-Integration etc.
Pro Pure and easy object orientation
Smalltalk is one of few languages that are purely object oriented. This provides a solid and easy to understand base on which to learn object oriented programming, the most popular approach to programming.
Pro Elegant syntax fits on a postcard
The syntax was designed to be easy enough for children to learn. Beginners can learn the language rules very quickly and then focus on programming without fighting the syntax at the same time. Things that have to be baked into the grammar in other languages are simple message sends with block arguments in Smalltalk. Expressions have only three precedence levels to worry about.
Pro Agile "interactive" test-driven development
Smalltalk had the original (and still the best) unit test system that inspired it in many other languages (like Java's JUnit). Working with interactive live objects in Smalltalk style TDD makes it easy to teach and learn TDD.
Pro Powerful integrated debugger
You can edit code and swap it in while the program is still running after an exception has already been signaled, or restart from anywhere in the call stack. You can inspect and modify the state of any object. Some Smalltalkers write unit tests and then program exclusively in the debugger.
Pro Internal source code and documentation
You can explore how everything works easily.
Pro Incremental compilation
Smalltalk provides an extremely fast code-compile-run-debug cycle. You don't have to stop and reset the world to tweak your program, since you can compile one method at a time while the environment is still running. This is great for beginners to experiment and prototype ideas.
Pro Inspired many other languages' object systems
Pro Open source
MIT licensed implementations Pharo, Squeak, Cuis & Dolphin
and GPL licensed GnuSmalltalk.
Pro Save and restore virtual machine image
A Smalltalk environment can save the state of a running program and later restore and resume execution. This includes the internal state of live objects, multiple thread stacks, and debugging sessions, making it easier for beginners to take the exact problem to an expert for assistance.
Pro Language uniformity
This leads to a very simple programming model (pure OO) that is still very powerful. A lot of stuff that is hard to implement in other languages is easier in Smalltalk.
Pro Graphical user interface
Beginners are usually stuck making command-line applications in other languages, because GUIs are too hard. Smalltalk GUIs are easy enough to start with.
Pro First-class functions with lexical closures
Also known as "blocks". These objects contain reusable snippets of code and as first-class objects they can be passed as arguments to other methods or blocks and also returned from them. "lexical closures" mean they retain access to the variables in the lexical environment they were written in, that is, in the surrounding code.
Pro It invented a lot of stuff
Smalltalk is the inventor of Just-in-Time compilation and the MVC concept, refactoring through their so-called refactoring browser and it was also one of the first adopters of a language virtual machine, closures, live programming, test driven development, an IDE and the development of GUI`s.
Pro As a first language, almost forces you to learn OO design
Hybrid languages (e.g., Java, C#, C++) make it easy to slip into procedural thinking. Smalltalk's pure OO approach makes it hard not to think in object-oriented terms. In addition, since the entire IDE and runtime components are there in the image for you to browse, you have plenty of examples of good OO design to learn from.
Pro Provides a functional way to interact with objects
Many languages today use object orientation, while the most of them stock on the half way in that perspective.
Smalltalk sees literally everything as an object and this includes things like the classes and primitive data types. There is are zero control structures such as selection and iteration, since all is done by sending messages to objects.
It use a lot of concepts from Lisp in order to provide a nice experience for this pure kind of object orientation.
It provides immutable data structures, closures, anonymous functions and higher order functions, while all those functions are objects. This is what makes Smalltalk so simple, elegant, and easy.
All this counts for Pharo, while other implementations as Amber are probably feature complete to it.
Pro No run-time exceptions
Lack of run-time exceptions makes it easy to produce large swathes of reliable front-end code without drowning in tests.
Pro Inferred static typing
ML static typing is great because it's always there, you just choose how explicit you want to be and how much you want the compiler to do.
Pro Super easy refactoring with very helpful compiler errors
In no other language you can refactor so easy without any worries, since the compiler will guide you through. It is like TDD but than compiler-error driven.
Pro Designed around high-level front-end development
As Elm was designed as a front-end langauge, it has out of the box support for things like DOM-element creation, letting programmers focus on their application logic, rather than implementation details specific to the web.
Pro Great and simple way to learn Purely Functional Programming
You can try to apply some functional programming ideas in other languages that have an imperative basis, but you haven't seen the real power unless you tried it in the environment of purely functional programming. Elm is a simple language with great learning resources and easy graphical output, which makes it easy to explore the power of functional programming. Plus programming in Elm is very readable.
Pro Good tooling
All major editors have great support. With Atom for example, Elm plugins are available for linting, formatting, make/compiler support and Elmjutsu will simply overflow you with super useful functions, like navigate to referenced definition and show expression type.
Pro Batteries included
The Elm Architecture means you don't need to spend valuable time and effort choosing the right frameworks, state management libraries, or build tooling. It's all built in.
Pro Static module system
Elm uses easy to use modules.
Use:
import List
import List as L
import List exposing (..)
import List exposing ( map, foldl )
import Maybe exposing ( Maybe )
import Maybe exposing ( Maybe(..) )
import Maybe exposing ( Maybe(Just) )
Creation:
module MyModule exposing (foo, bar)
Pro Missing syntactic sugar
Easy to learn, most functions have only one way, not 5 alternatives where you must study where to best use what.
Pro Growing community
Pro Interactive Programming and Hot Swapping
Support for hot swapping and interactive programming is included.
Pro Easy to code review
The lack of side-effects and simple, consistent language semantics make it easy to quickly review incoming changes.
Pro Higher confidence in code correctness and quality
Pure functions, immutable data structures, amazing compiler, clean and homologous syntax used for HTML, logic, and optionally to replace CSS, elimination of entire classes of bugs so you don't even need most unit tests. These factors lead to better code, better programs, higher confidence, and ultimately, more satisfaction.
Pro Not quite Haskell semantics
Luckily you do not have to learn Haskell to be able to do any Elm. It is meant to be a language that compiles to Javascript, so for Javascript programmers (Front end) not for CS students who want to learn as many different algorithms as possible.
Cons
Con OO is becoming obsolete
Smalltalk did it best, but the whole paradigm is a poor fit for the expected future multicore processors. Isolated mutable variables with no compile checks is a recipe for race conditions in multithreaded code. Beginners would be better off learning a functional language.
Con Not common
Smalltalk missed an opportunity to become mainstream when its implementations cost $5000 per seat versus $0 open source. New open source implementations (Pharo, Squeak) have minor corporate backers but not yet an IT behemoth. Direct jobs are scarce (but indirectly Smalltalk experience is very well regarded). Online communities are relatively small.
Con Not useful for mobile development
While Smalltalk is very powerful and easy to learn, it doesn't have a well supported mobile distribution, but you'll be spoiled for working in mainstream languages like Java, Swift or Kotlin where jobs are more readily available.
Con Virtual machine in its own isolated world
Smalltalk wants to be the whole OS. While this has tremendous advantages internally, interacting with the world outside the VM is not as easy as pure Smalltalk and must be done via a Foreign Function Interface.
Con Non-standard arithmetic ordering
Since every operation is considered a message sent sent is a specific order, all arithmetic operators have the same precedence. E.g. 2 + 3 x 4 translates to 2 + 3, and the result is multiplied by 4, giving an answer of 24 (instead of the correct answer - 14). Once you are learn this, it can easily handled using brackets, e.g. 2 + (3 x 4), but still a momentary suprise for beginners.
Con Lack of typeclasses
Elm doesn't have typeclasses which means some code needs to be duplicated. A fix in a function that needs typeclasses means all of the duplicates need to be fixed too.
Con limited js interop
only one way ports are available as a crude js FFI. This means you can only call functions both directions but will not get a result.
Con Harder to get buy-in from devs and mgmt
It's a total divergence from what most people are used to in the JS ecosystem. The change in syntax can be scary, the change in approaching problems can be scary. The fact that it's not backed by FANG can be scary. The fact that it's not v1.0 can be scary. The governance model and the deliberately slow release cadence can be scary. There are a couple harsh medium articles, hackernews/reddit posts out there made by people with an ax to grind that can be scary if you don't have a better picture of the Elm community, the tradeoffs that have been made, or the benefits to be had over other options. None of these are good reasons to write off further investigation of a great tech, but it happens.
Con Code Repetition
Because of the lack of genericness Elm needs a lot of code to be repeated. There are 130+ implementations of map in elms core libraries.
Con Features get removed without warning
Often features that are deemed to be misused by the community like infix operators get removed without much of a warning.
Con Community harsh if criticised
If one even dares to start a discussion about a feature on elms slack, discord, subreddit or github one will be aggressively shut down often argueing that one should use purescript instead
Con Poor Windows support
Few if any of Elm's core contributors are Windows users and breaking bugs are sometimes left for weeks or months.
Con Good for beginners not good for experts
Development in elm is quite nice until you need some more advanced features. These however are actively discontinued and removed because elm wants to establish a "single way of doing things" philosophy
Con Updates break existing code often
The last few updates of elm broke existing code in major ways.
Con Adds an additional layer of abstraction
Some users claim that Elm adds an additional layer of abstraction, meaning that it is one more hurdle between the brain and the product.
Con Functional programming itself has quite a steep learning curve
Functional programming can be quite difficult to get your head around. It takes time to unlearn object orientational habits.
Con No Genericness in the future
Currently there is no code genericness like typeclasses possible, it has been officially stated that this will never change.
Con Not database-friendly
It is lots of work to make a server or database your "one source of truth", as Elm makes you write endless JSON parse boilerplate to talk to the server.
Con No Syntactic Sugar
Often you need to write longer and less readable code because there are no alternatives that are more concise.