Learn to Program(2)

Learn to Program(2)

6. Flow Control
6.1 Comparison Method
puts 'cat' < 'dog'
result is true, because cat comes before dog in the directory.

6.2 Branching
That is branching, if what comes after the if is true, we run the code between the if and the end. If what comes after the if is false,
we don't.
if name == 'carl'
   puts 'that is an nice name'

6.3 Looping
command = ''
while command != 'bye'
puts command
command = gets.chomp
end
puts 'The program comes an end'

7 Arrays and Iterators
[], [5], ['Hello', 'Goodbye'], [89.9, 'test', [true, false]]
names = ['Ada', 'Belle', 'Chris']
puts '1' + names.to_s
puts '2' + names[0]
puts '3' + names[1]
puts '4' + names[2]
1["Ada", "Belle", "Chris"]
2Ada
3Belle
4Chris

7.1 The Method each
each allows us to do something (whatever we want) to each object the array points to.
languages = ['English', 'German', 'Ruby']
languages.each do |lang|
    puts 'I love ' + lang + '!'
end

I love English!
I love German!
I love Ruby!

3.times do
  puts 'go'
end
go go go

7.2 More Array Methods
foods = ['artichoke', 'brioche', 'caramel']
puts foods.to_s
puts foods.join(', ')

["artichoke", "brioche", "caramel"]
artichoke, brioche, caramel

200.times do
puts []
end

puts an empty array 200 times means nothing.

favorites = []
favorites.push 'carl'
favorites.push 'kiko'
puts '0         =' + favorites[0]
puts 'last      =' + favorites.last
puts 'length    =' + favorites.length.to_s
puts 'pop       =' + favorites.pop
puts 'length    =' + favorites.length.to_s

0         =carl
last      =kiko
length    =2
pop       =kiko
length    =1

8. Writing Your Own Methods
def sayHello
  puts 'say hello to everyone!'
end
sayHello
sayHello

say hello to everyone!
say hello to everyone!

8.1 Method Parameters
def saysomething words
  puts 'my words: ' + words
end
saysomething 'carl is a good boy'

my words: carl is a good boy

8.2 Local Variables
We can access the variable, but we can not screw them up.
def saysomething words
  words = 'nothing'
  puts 'my words: ' + words
end
words = 'carl is here'
saysomething words
puts words

my words: nothing
carl is here

8.3 Return Values
puts always returns nil. Every method has to return something, even if it's just nil.
def saysomething words
  puts 'my words: ' + words
  'result value'
end
words = 'carl is here'
result = saysomething words
puts result
my words: carl is here
result value

references:
http://pine.fm/LearnToProgram/?Chapter=06