Some may say Ruby is a bad rip-off of Lisp or Smalltalk, and I admit that. But it is nicer to ordinary people. — Yukihiro “Matz” Matsumoto, LL2

When I heard the Smalltalk traits of Ruby, I was intrigued. When I learned more, I enjoyed Ruby’s similarities with one of the most beautiful and powerful languages I’ve known. As I dug deeper, I enjoyed more of its wonderful metaprogramming abilities, which makes Ruby’s classes a lot more dynamic and easy to declare than Smalltalk’s. After reading this in-depth comparison of both, and Kent Beck’s article on the incompatibilities of Smalltalk’s VM implementations, I realized that I was generally more in favor of Ruby than Smalltalk (even though I fear that What Killed Smalltalk Could Kill Ruby, Too).

But Ruby is not perfect. In all fairness, its creator claims that it’s just plain impossible to design a perfect language. But I do believe it could be a bit better. People do point out some controversial rough edges, but these seem a bit trifle when compared to what really bothers me:

No scoped open classes. It is an issue that is actually being considered to be solved on 2.0 (and there are some branches of ruby that enable it), but, for the time being, there is no way to make the changes made by opening an existing class only apply to objects while being used on the a lexical scope. This is not the same as adding and removing the changes as, in this case, calls that fall out of scope (such as to another module or file) still see the changes. It would be nice to have both ways of open classes: scoped and not scoped.

Method arguments do not interleave with the method’s name (like in Smalltalk). Example: Instead of calling: File.fnmatch(‘*’, ‘/’, File::FNM_PATHNAME) you’d be to call it like: File.fn match: ‘*’ path: ‘/’ flags: File::FNM_PATHNAME. This seems weird, but it is a very powerful feature that allows method invocation to be descriptive, similar to Python’s named arguments or even Ruby’s named arguments with a hash. On the other hand it has a cleaner syntax than the former, and does not require checking hash keys as the later (the later is still useful for methods that want to receive an arbitrary list of named arguments). It would change a bit of the syntax of method_missing and how to deal with varargs and blocks for each parameter, but these can be dealt with as Scala does with its parameter lists.

There is no method called (). Procs (who are the obvious beneficiaries of such change ) use the method call, but one could be an alias to the other. There would be a mild ambiguity here, when you call the function that was just returned. For instance, imagine func is a method that receives no arguments and returns a function (that is: an object that implements the () method) wich also receives no arguments. Then func() could mean 1. call func, and 2. call the function returned by func. I am aware this is kinda of a sensitive topic, but the Scala approach to this issue is very simple: func and func() are the same (provided func can be called with no parenthesis). If you want to call the returned function in the same expression, use func()(). With the alias, you’d be able to call it like func.call() , func().call() or even func.call



No way to create simple blocks. It would be nice to have something similar to Scala’s underscore or Groovy’s it, which allows method invocations like: collection.map(get_square_of(_)) in Scala and collection.map(get_square_of(it)) in Groovy. Ruby’s symbol coercion to proc (&:method) does not really work on anything besides methods of the arguments of the block.

Difficulties of composing callback methods. You could be sure to always invoke super on them, and even meta-program all the classes/objects that do not do such thing. However, it is not easy to actually see which methods will be called, or even manipulate/re-prioritize the blocks of code on runtime (kinda like a Chain of Responsibility), which can be very bad, as these methods can modify a lot of behaviour throughout the Object Space.

The reflection API could be more thorough. For instance, you can’t get the source code of a method/class, etc (as you can in Python). You can use Parse Tree and Ruby2Ruby to do it, but Parse Tree is not portable (does not even work on ruby 1.9) and the output can be formated differently than the actual source code (which can be critical on DSLs). Also, methods added do not have information on which line of code they were added (which is less important when adding methods the recommended way: extending/including Modules), and properties created with class methods (such as those created by attr_reader, or some other libraries equivalents) can’t be discovered on runtime (they are like any other method, with no other meta-data whatsoever). Ruby also seems to be missing some helper methods, such as #metaclass.

No support for immutability. This is kinda nitpicking, but using recursive freeze (as noted by Dean Wampler) is not really practical (as it is really slow). Neither does it encompass immutable local variables. This is not only useful for concurrency and functional programming issues, but is also useful when writing code that is side-effect free so that it is easier to reason about.

The return value of a setter method (that is: one that ends with the equals symbol) is the argument, not the return value of the method. This is an issue that matters more when using immutable objects, as the only way for them to “mutate” is to return a new object. Therefore you can’t use a setter method on an immutable object, as, even if it returns a new one, the runtime will ignore the return value and set to the variable the argument that was received. On the other hand, I don’t think this can be changed without breaking a lot of existing code.

Several of this annoyances can be solved with a heavy dose of open classes, s-expressions manipulation (using Parse Tree) and meta-programming in general. Knuth has said that: Language designers also have an obligation to provide languages that encourage good style, since we all know that style is strongly influenced by the language in which it is expressed. Fully agreeing with such Sapir-Whorf-esque sentence, I feel it would be a good thing if the underlying listed solutions were built into the language itself (and supported across implementations, such as JRuby, Iron Ruby, Rubinius, Maglev), as it would not only improve, even if a little bit, the language itself, but also they way its users write code.

Update: Thanks Michael Fellinger for noting that ruby blocks are fully adherent to method definitions on 1.9, as they allow both default parameters and blocks as arguments.