Why I still like Ruby

Some years ago Ruby in conjunction with rails was an absolute hype. In the Rails User Group in Zürich we had meetups with 30 people every two weeks. The meetings every two weeks have been retained, but often we are just five to ten people now. Is the great time of Ruby over or is it just a temporary decline? Is Perl 6 now taking over, since it is ready?

Perl 6 is cool and could challenge Ruby and it is now getting more and more towards production readiness. This will happen next year. This is what we will say next year. But Perl 6 is or will be very cool, stay tuned… What about Perl 5? At least Allison Randall still likes Perl (5). But it has other areas of strength than Ruby, so I will leave my opinionated writing focused on Ruby.

But the hype is right now in the area of JavaScript.

There are approaches to use server side JavaScript, which are interesting, because JavaScript needs to be dealt with on the client anyway and then it is tempting to have the same language on both sides.

There are also approaches to move back from the server to the client and put more functionality into the client and make the server less relevant, at least the percentage of development effort of the client gets more and of the server gets less.

There are cool frameworks for the client development in JavaScript and in conjunction with HTML5 and these frameworks a lot can be achieved.

On the other hand we are exploring NoSQL-databases like MongoDB and MongoDB is using JavaScript with some extension library as query language.

The general hype is toward functional programming and voila, JavaScript is functional, it is the most functional of the languages that have been established for a long time and brought the functional paradigm to every developer and even to the more sophisticated web designer, everything under the radar and long time before we knew how cool functional programming is. On the other hand, Ruby (and by the way Perl and especially Perl6) allow programming according to the functional paradigm as well, if used appropriately. But in JavaScript it is slightly more natural.

Then we have more contenders. Java is not dying so soon and it is still strong on its web frameworks, JavaServerFaces and one million others, not so bad actually.

And the idea of rails or at least its name, has been taken over by the groovy guys to develop groovy on grails, which integrates nicely with a Java enterprise backend.

And the more functional languages like F#, Scala, Haskell, Erlang, Elixir (and some others for the guys that don’t find Haskell theoretical enough) are around and gaining or retaining some popularity. Will Scala support the Erlang-VM as alternative backend, like JavaScript and JVM are supported today (and dotnet-CLI in the past)? And Scala has a promising web framework with play, that does WebServices right, which is what is actually needed for the modern client side JavaScript frameworks, just as an example.

PHP was always the ugly baby, why did they implement a second Perl based on the subset of Perl they understood? Well, I am not advocating PHP at all, but there are some pretty decent PHP-applications that are working really well with high load, like Wikipedia.

The unequal twin of Ruby, Python, is doing pretty well as well on attempting to get a web framework called Django. I have not investigated it at all, but it seems to exist.

So, where is ruby and rails? Ruby is a beautiful language, that has done many things better than any of the languages mentioned here:

It is easy to learn.

It has a nice and complete and consequent concept for object orientation.

It allows all the functional programming, most of it pretty natural.

It has decent numerical types by default. Integer grow to arbitrary length, Rationals are included and Complex numbers are included. JavaScript does not even have integers, it just has one numerical type: double precision floating point.

It allows extending, even operator overloading for new numerical types.

And it has a useful and easily accessible web framework like rails and actually some contender as alternative web frameworks, like camping, sinatra and some others.

And the development effort and the amount of code needed for a certain functionality is still lower than in Java or C# or COBOL.

I do believe that the web applications that are mostly server based and are using just HTML or minimal JavaScript still have their place and will be discovered again as useful for many application areas.

To conclude, I think that Ruby did not make it to become the replacement for Java, that some saw in it and that was due according to the history of replacement of other mainstream languages that have moved to legacy in the past. But I do believe that it will play an important role for some years to come and beyond the current JavaScript hype. Off course it will be challenged again in the future and maybe something will replace the main stream and will make Ruby on Rails just another legacy area for web applications. But I don’t even have an idea what that will be. I don’t think JavaScript. Perl6, Scala, F# or Clojure do have technical potential to do so, but I do not see that happening in the near future. Maybe something new will come up? Or something old? Just remember, Ruby is about as old as Java.

We will see.

Read more in this discussion on Quora.

For those who are interested, I actually teach Ruby and it is possible to arrange trainings for two to five days, depending on the previous knowledge of the participants and the goals.

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Monads in Ruby

Monads? Easy!

A Monad over X simply is a Monoid in the Category of Endofunctors of X.

Monads? Really!

  • Monads are a concept in mathematics
  • Algebra is an area of mathematics
  • Category theory is an abstraction of algebra.
  • Monads are defined in category theory
  • Remember: in category theory we talk about infinity beyond cardinality of infinite sets…
  • The „idea“ has been transplanted into something used in programming languages…
  • Just think of stars in terms of astronomy, in terms of decoration and in terms of music or movies

Monad as Design Pattern

  • Actually Monads should be viewed as a design pattern
  • That describes the level of abstraction

Motivation

  • Pure functional programmers are poor guys when it comes to state
  • State is evil
  • State is not possible or hard
  • I/O is state, actually a segment of the outer world is manipulated
  • Monads encapsulate that
  • Even if you are happy with state (poor IT theology…):
    Multilevel nil problem 🙁

Monads in Functional Programming

  • Container type
  • wrap(foo):
    • class method
    • can also be called unit
    • Btw. arrogant Haskell guys call it return
  • pass(&block)
    • instance method
    • Can also be called bind
  • Optionally more operations (mjoin, empty, +,…)

Identity Monad

class Identity
    def initialize(value)
      @value = value
    end
end

def Identity.wrap(value)
  new(value)
end

class Identity
    def pass
        yield @value
    end
end

Axioms

  • Left-identity for pass:
    Calling pass on a newly wrapped value is the same as applying the block to that value
  • Right-identity for pass:
    Calling pass with a block that only calls wrap on its parameter results in the same as its target object
  • Nesting:
    Nesting pass blocks should be equivalent to calling them in sequence.

Does our Monad survive 1st law?

Identity.wrap(foo).pass do |value|
  f(value)
end

Is equivalent to

f(foo)

That is how we defined pass.

Does our Monad survive 2nd law?

bar.pass do |value|
  Identity.wrap(value)
end

Is equivalent to

bar

That is how we defined pass.

Does our Monad survive 3rd law?

bar.pass do |value_a|
    f(value_a)
end.pass do |value_b|
    g(value_b)
end

Is equivalent to

bar.pass do |value_a|
  f(value_a).pass do |value_b|
    g(valueb)
  end
end

That is how we defined pass.

Array as Monad

def Array.wrap(value)
    [ value ]
end

class Array
    def mjoin
        inject([]) { |combined, arr| combined + arr }
    end

    def pass(&block)
        map(&block).mjoin
    end
end

Does it work?

Have a look yourself…

More Monad Operations

Empty:

def Array::empty
    []
end

+:

Already there

Other Examples

  • Option (Some, None)

Links & Sources

This article is based on a speach given in the Ruby on Rails user group Switzerland.

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Residue Class Rounding

Deutsch

If you do not know what residue classes are, just read on, it will be explained to the extent needed later on.

The concept of rounding seems familiar, but let us try to grab it a little bit more systematically.

Let us assume a set M of numbers and a subset N \subseteq M of it, whose elements can be represented in the programming or software environment we are having in mind. We want to use a metric d : M \times M \rightarrow \Bbb R_+, (x, y) \mapsto r=d(x,y)>=0. Usually we have three requirements for d:

  • Identity of indiscernibles: d(x,y) = 0 \iff x = y
  • Symmetry: d(x,y)=d(y,x)
  • Triangular inquation: d(x,z) \le d(x,y) + d(y,z)

Usually the number that we are dealing with can be considered to be within the world of real or complex numbers, we can hence assume that M \subseteq \Bbb C, often even M \subseteq \Bbb R or if we are honest M \subseteq \Bbb Q. Then we are usually working with d(x,y) = |x-y|, which is kind of implicitly clear. If you do not know complex numbers, just think of real or even rational numbers, which is the most common case anyway. Off course the concepts for rounding of p-adic numbers are really interesting and beautiful, but since I do not want to explain p-adic numbers here, I will not extend on this issue.

What is our intuitive understanding of rounding?
Maybe just a map
r: M \rightarrow N, x \mapsto r(x),
that is chosen with certain constraints for each x in such a way that d(x, r(x)) is minimal.
We need the constraints to enforce uniqueness if multiple values y\in N with minimal d(x,y) exist. The classical case of rounding to integral numbers has to answer the question of how to round 0.5. If N is a subset of the real numbers, which is „usually“ the case, we have ordering. We can choose between the following constraints:

ROUND_UP
|r(x)|\ge |x| Z.B. r(0.4)=1 and r(0.5)=1 and r(-0.5)=-1
ROUND_DOWN
|r(x)|\le |x| Z.B. r(0.6)=0 and r(0.5)=0 and r(-0.5)=0
ROUND_CEILING
r(x) \ge x Z.B. r(0.4)=1 and r(0.5)=1 and r(-0.5)=0
ROUND_FLOOR
r(x) \le x Z.B. r(0.6)=0 and r(0.5)=0 and r(-0.5)=-1
ROUND_HALF_UP
Minimize d(r(x),x), but if multiple optimal values exist for r(x), pick the one furthest away from 0, for example r(0.4)=0 and r(0.6)=1 and r(0.5)=1 and r(-0.5)=-1
ROUND_HALF_DOWN
Minimize d(r(x),x), but if multiple optimal values exist for r(x), pick the one closest to 0, for example r(0.4)=0 and r(0.6)=1 and r(0.5)=0 and r(-0.5)=0
ROUND_HALF_CEILING
Minimize d(r(x),x), but if multiple optimal values exist for r(x), pick the largest, for example r(0.4)=0 and r(0.6)=1 and r(0.5)=1 and r(-0.5)=0
ROUND_HALF_FLOOR
Minimize d(r(x),x), but if multiple optimal values exist for r(x), pick the smallest, for example r(0.4)=0 and r(0.6)=1 and r(0.5)=0 and r(-0.5)=-1
ROUND_HALF_EVEN
Minimize d(r(x),x), but if multiple optimal values exist for r(x), pick the one with even last digit. Please observe that this constraint is useful in the classical case, but it cannot be generalized. For example: r(0.4)=0 and r(0.6)=1 and r(0.5)=0 and r(-0.5)=0 and (1.5)=2
ROUND_UNNECESSARY
This constraint does not work in the mathematical sense (or only with ugly abusive math formulas), but programmatically we can do that: We try r(x)=x and throw an exception if not x\in N.

Usually we are thinking in the decimal system (even though our computers prefer something else, but the computer should serve us and not vice versa..). So we pick a power of ten 10^n with n \in \Bbb N_0, so n \ge 0. Now we simply define
N = \{ x \in M : 10^n x \in \Bbb Z\},
which means that N contains all numbers of M with a maximum of n digits after the decimal point. This rounding works quite well with something like LongDecimal in Ruby or BigDecimal in Scala or Java, but BigDecimal offers fewer rounding modes than LongDecimal for Ruby.

Now we look at the residue class rounding. We assume such a power of ten 10^n. Then we need an integral number m \ge 2 and a set of numbers R \subseteq \{0,...,m-1\}, we call them residues. Now we define N = \{ x \in M : 10^n x \in {\Bbb Z} \wedge \bigvee_{r \in R} 10^n x \equiv r \mod{m}\}.
That means that if we fill the number with zeros to the given number of places after the decimal point, remove the decimal point and perform a division with residue of this number by m, the residue lies in R. In this case ROUND_HALF_EVEN can become difficult to implement and ambiguous, so we might need to sacrifice it. But even worse, we have to deal with the case that 0 is not in R and provide rules how to round 0. The candidates have self-explanatory names:

  • ZERO_ROUND_TO_PLUS
  • ZERO_ROUND_TO_MINUS
  • ZERO_ROUND_TO_CLOSEST_PREFER_PLUS
  • ZERO_ROUND_TO_CLOSEST_PREFER_MINUS
  • ZERO_ROUND_UNNECESSARY

An important application of this is m=10 and R=\{0, 5\}. This is used in Switzerland and probably other currency regions for rounding money amounts to multiples of 5 Rappen (0.05 CHF). This has already been described in „Rounding of Money Amounts„. If we have m=10 and R=\{0,1,2,3,4,5,6,7,8,9\} we have the usual non-CHF-rounding case. Maybe there are even cases for m=10 and R=\{0,2,4,6,8\}. But the concept is more general, if you like to use it.

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Rails 4.0 Beta

Rails 4.0 Beta. 😉

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Ruby 2.0 coming soon

This is a translation of Ruby 2.0 in Sicht

According to blade.nagaokaut.ac.jp Ruby 2.0 is almost finished. The new features are already known and a release 2.0.0-p0 is planned for Q1 2013.

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