Scala loops

Today, I finally got to play with Scala. I’ve been using mainly Ruby (and loving it) for most of my projects but I promised myself (in one of my new year’s resolution) that I will learn a new programming language this year. So from time to time, I will sprinkle this blog with some Scala love.

Now, for some mandatory hello world program. Nah. The code below simply prints the arguments to your Scala program.

var i = 0
while (i < args.length) {
  println("hello " + args(i) + "!")
  i += 1
}

// Assuming you have saved the code in hello.scala, do the following to run the code:
// scala hello.scala arg1 arg2 arg3

The code above is an imperative style used normally in languages like C or C++. Most new programmers are exposed to this style.

Being a Ruby developer, I quickly wondered if there is something similar to “.each” method? Yes, there is.

args.foreach(arg => println(arg))
args.foreach(println)

Above is a functional style and is something you will be comfortable with as you improve your programming skill. In Scala, the second line is possible if the function accepts a single argument.

Since ‘println’ is just a function, you could just replace it with your own function.

def printer(x: String) = {
  println(x.toUpperCase)
}

args.foreach(arg => printer(arg))

Yes, you guessed right. You can also define anonymous function.

args.foreach(arg => { println(arg.toUpperCase) })

When I first heard that Scala is somewhat related to Java, my first thought was it is going to be another verbose language. Well, I was wrong It appears to be a fun and powerful language worth learning.

24 Ruby tips and tricks

Peter Cooper will share more tips in his book to be released later this year. Stay tune and don’t forget to leave your email address to get updates at http://rubyreloaded.com/trickshots/

Here are some of the tips in the video.

Generate random numbers within a given range

irb(main):019:0> rand(10..20)
=> 12
irb(main):020:0> rand(10...20) # works with exclusive range
=> 16

Dump your object using awesome_print

# Install the gem first
gem install awesome_print

irb(main):001:0> require 'ap'
=> true
irb(main):002:0> ap :a => 1, :b => 'greg', :c => [1,2,3]
{
    :a => 1,
    :b => "greg",
    :c => [
        [0] 1,
        [1] 2,
        [2] 3
    ]
}
=> {:a=>1, :b=>"greg", :c=>[1, 2, 3]}

Concatenating strings

irb(main):005:0> "abc" + "def"
=> "abcdef"
irb(main):006:0> "abc".concat("def")
=> "abcdef"
irb(main):007:0> x = "abc" "def"
=> "abcdef"

Include modules in a single line

class MyClass
  include Module1, Module2, Module3
  # However, the modules are included in reverse order. Confusing eh!
end

Instance variable interpolation

irb(main):008:0> @name = "greg"
=> "greg"
irb(main):009:0> "my name is #{@name}"
=> "my name is greg"
irb(main):010:0> "my name is #@name"
=> "my name is greg"

I still prefer the use curly braces.

Syntax checking

➜  ruby -c facu.rb 
facu.rb:12: syntax error, unexpected keyword_end, expecting $end

Zipping arrays

irb(main):027:0> names = %w(fred jess john)
=> ["fred", "jess", "john"]
irb(main):028:0> ages = [38, 47,91]
=> [38, 47, 91]
irb(main):029:0> locations = %w(spain france usa)
=> ["spain", "france", "usa"]
irb(main):030:0> names.zip(ages)
=> [["fred", 38], ["jess", 47], ["john", 91]]
irb(main):031:0> names.zip(ages, locations)
=> [["fred", 38, "spain"], ["jess", 47, "france"], ["john", 91, "usa"]]

Range into arrays

irb(main):034:0> (10..20).to_a  # what I used to do
=> [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
irb(main):035:0> [*10..20]
=> [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

Using parameter as default value

irb(main):047:0> def method(a, b=a); "#{a} #{b}"; end
=> nil
irb(main):048:0> method 1
=> "1 1"
irb(main):049:0> method 1, 2
=> "1 2"

Put regex match in a variable

irb(main):058:0> s = "Greg Moreno"
=> "Greg Moreno"
irb(main):059:0> /(?<first>\w+) (?<second>\w+)/ =~ s
=> 0
irb(main):060:0> first
=> "Greg"
irb(main):061:0> second
=> "Moreno"