respuestas.txt

18. 2.0.0p247 :001 > puts "Hello world" Hello world
 => nil 
2.0.0p247 :002 >


21.
La diferencia al ejecutar un programa con el intérprete de Ruby y el
 irb, es que el primero nos muestra por pantalla la cadena de
 caracteres que hemos introducido en el programa sin nada más y el
 segundo nos muestra la cadena de caracteres y nil, permitiendonos
 seguir introduciendo sentencias en el terminal.


26.

 6: 
     7: #set x to 10
     8: x = 10
     9: 
    10: #start a PEPL session
 => 11: binding.pry
    12: 
    13: #program resumes here (after pry session)
    14: puts "program resumes here. Value of x is: #{x}."

[1] pry(main)> puts x
10
=> nil
[2] pry(main)> def hello
[2] pry(main)*   puts "Hello world"
[2] pry(main)* end  
=> nil
[3] pry(main)> hello
Hello world
=> nil
[4] pry(main)> byebye
bye bye World!!!
=> nil
[5] pry(main)> x = "changed"
=> "changed"
[6] pry(main)> exit
program resumes here. Value of x is: changed.

27.

Con PRY, al utilizar binding.pry, nos abre una consola alternativa
 donde podemos ver que datos tenemos hasta ese momento e incluso
 podemos modificar el programa. Con el intérprete interactivo se
 ejecutar el programa y me permite introducir sentencias y se van
ejecutando.


34.

La diferencia entre "\t\n" y '\t\n' es que con la primera utilizamos
comillas dobles y nos permite realizar un tabulador y un retorno de
carro respectivamente sin salir nada por pantalla. En el segundo caso
utilizamos unas comillas simples que nos permiten visualizar por
pantalla tanto \t como \n.


35.

El %q nos permite no interpolar las cadenas, escribiéndolas de forma
literal.

Si introducimos %q{hello world\} nos motrará por pantalla
 "hello wordl\n". Si introducimos %q{'a' 'b' 'c'} mostrará
 "'a' 'b' 'c'".

36.

El %Q nos permite devolver la cadena e interpola.

Si introducimos %Q{hello world\n} mostrará "hello world" y hará un
retorno de carro. Si introducimos %Q{"a" "b" "c"} mostrará 
""a" "b" "c"".


37.

En c quedará "--4--\n--2--\n"


38.

En c quedará "--\#{a}--\n--\#{b}--\n"

39

s[0,2] => "he" 
s[-1,1] => "o" 
s[0,10] => "hello" 

40.

En g quedará "hello world" 

41.

En e quedará "..."

42.

El resultado será "2 2 2 "

43.

Muestra:

this
is
a
test

44.

Muestra sus componentes sin interlpolar:

\t
\n

45.

No muestra nada por pantalla ya que interpola tanto el tabulador como
el retorno de carro.


46.

Contiene un vector con elementos nulos: [nil, nil, nil]

47.

Contiene un vector con tres elementos: [0, 0, 0]


48.

En b quedará [[1, 2], [3, 4]]


49.

En c quedará [0, 2, 4]

50.

 > a = ('a'..'e').to_a
 => ["a", "b", "c", "d", "e"] 
 > a[1,1]
 => ["b"] 
 > a[-2,2]
 => ["d", "e"] 
 > a[0...1]
 => ["a"] 
 > a[-2..-1]
 => ["d", "e"] 

51.

 > a
 => ["a", "b", "c", "d", "e"] 
 > a[0,2] = %w{A B}
 => ["A", "B"] 
 > a
 => ["A", "B", "c", "d", ""] 
 > a[2..5] = %w{C D E}
 => ["C", "D", "E"] 
 > a
 => ["A", "B", "C", "D", "E"] 
 > a[0,0] = [1,2,3]
 => [1, 2, 3] 
 > a
 => [1, 2, 3, "A", "B", "C", "D", "E"] 
 > a[0,2] = []
 => [] 
 > a
 => [3, "A", "B", "C", "D", "E"] 
 > a[-1,1] = [ 'Z' ]
 => ["Z"] 
 > a
 => [3, "A", "B", "C", "D", "Z"] 
 > a[-2,2] = nil
 => nil 
 > a
 => [3, "A", "B", "C", nil]


52.

2.0.0-p247 :001 > a = (1...4).to_a
 => [1, 2, 3] 
2.0.0-p247 :002 > a = a + [4, 5]
 => [1, 2, 3, 4, 5] 
2.0.0-p247 :003 > a += [[6, 7, 8]]
 => [1, 2, 3, 4, 5, [6, 7, 8]] 
2.0.0-p247 :004 > a = a + 9
TypeError: no implicit conversion of Fixnum into Array
	from (irb):4:in `+'
	from (irb):4
	from /usr/local/rvm/rubies/ruby-2.0.0-p247/bin/irb:13:in `<main>'


53.

2.0.0-p247 :001 > x = %w{a b c d a}
 => ["a", "b", "c", "d", "a"] 
2.0.0-p247 :002 > x = x - %w{b c d}
 => ["a", "a"] 


54.

2.0.0-p247 :001 > z = [0]*8
 => [0, 0, 0, 0, 0, 0, 0, 0] 

55.


2.0.0-p247 :001 > a = []
 => [] 
2.0.0-p247 :002 > a << 1
 => [1] 
2.0.0-p247 :003 > a << 2 << 3
 => [1, 2, 3] 
2.0.0-p247 :004 > a << [4, 5, 6]
 => [1, 2, 3, [4, 5, 6]] 
2.0.0-p247 :005 > a.concat [7, 8]
 => [1, 2, 3, [4, 5, 6], 7, 8] 


56.


2.0.0-p247 :001 > a = [1, 1, 2, 2, 3, 3, 4]
 => [1, 1, 2, 2, 3, 3, 4] 
2.0.0-p247 :002 > b = [5, 5, 4, 4, 3, 3, 2]
 => [5, 5, 4, 4, 3, 3, 2] 
2.0.0-p247 :003 > c = a | b
 => [1, 2, 3, 4, 5] 
2.0.0-p247 :004 > d = b | a
 => [5, 4, 3, 2, 1] 
2.0.0-p247 :005 > e = a & b
 => [2, 3, 4] 
2.0.0-p247 :006 > f = b & a
 => [4, 3, 2] 


57.


2.0.0-p247 :001 > a = 1..10
 => 1..10 
2.0.0-p247 :002 > a.class
 => Range 
2.0.0-p247 :003 > a.to_a
 => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
2.0.0-p247 :004 > b = 1...10
 => 1...10 
2.0.0-p247 :005 > b.to_a
 => [1, 2, 3, 4, 5, 6, 7, 8, 9] 
2.0.0-p247 :006 > b.include? 10
 => false 
2.0.0-p247 :007 > b.include? 8
 => true 
2.0.0-p247 :008 > b.step(2) {|x| print "#{x} "}
1 3 5 7 9  => 1...10 
2.0.0-p247 :009 > 1..2.to_a
NoMethodError: undefined method `to_a' for 2:Fixnum
	from (irb):9
	from /usr/local/rvm/rubies/ruby-2.0.0-p247/bin/irb:13:in `<main>'

58.


2.0.0-p247 :001 > r = 0...100
 => 0...100 
2.0.0-p247 :002 > r.member? 50
 => true 
2.0.0-p247 :003 > r.include? 99.9
 => true 
2.0.0-p247 :004 > r.member? 99.9
 => true 

59.


2.0.0-p247 :001 > true.class
 => TrueClass 
2.0.0-p247 :002 > false.class
 => FalseClass 
2.0.0-p247 :003 > puts "hello" if 0
hello
 => nil 
2.0.0-p247 :004 > puts "hello" if nil
 => nil 
2.0.0-p247 :005 > puts "hello" if ""
(irb):5: warning: string literal in condition
hello
 => nil 


60.


2.0.0-p247 :001 > x = :sym
 => :sym 
2.0.0-p247 :002 > x.class
 => Symbol 
2.0.0-p247 :003 > x == 'sym'
 => false 
2.0.0-p247 :004 > x == :sym
 => true 
2.0.0-p247 :005 > z = :'a long symbol'
 => :"a long symbol" 
2.0.0-p247 :006 > z.class
 => Symbol 
2.0.0-p247 :007 > x == 'sym'.to_sym
 => true 


61.


2.0.0-p247 :001 > s = "Ruby"
 => "Ruby" 
2.0.0-p247 :002 > t = s
 => "Ruby" 
2.0.0-p247 :003 > t[-1] = ""
 => "" 
2.0.0-p247 :004 > print s
Rub => nil 
2.0.0-p247 :005 > t = "Java"
 => "Java" 
2.0.0-p247 :006 > print s, t
RubJava => nil 


62.


2.0.0-p247 :001 > "%d %s" % [3, "rubies"]
 => "3 rubies" 


63.


2.0.0-p247 :001 > x, y = 4, 5
 => [4, 5] 
2.0.0-p247 :002 > z = x > y ? x : y
 => 5 
2.0.0-p247 :003 > x,y,z = [1,2,3]
 => [1, 2, 3] 


64.


2.0.0-p247 :002 > x = { :a => 1, :b => 2 }
 => {:a=>1, :b=>2} 
2.0.0-p247 :003 > x.keys
 => [:a, :b] 
2.0.0-p247 :004 > x.values
 => [1, 2] 
2.0.0-p247 :005 > x[:c]=3
 => 3 
2.0.0-p247 :006 > x
 => {:a=>1, :b=>2, :c=>3} 
2.0.0-p247 :007 > x.delete('a')
 => nil 
2.0.0-p247 :008 > x
 => {:a=>1, :b=>2, :c=>3} 
2.0.0-p247 :009 > x.delete(:a)
 => 1 
2.0.0-p247 :010 > x
 => {:b=>2, :c=>3} 
2.0.0-p247 :012 > x = { :a => 1, :b => 2, :c => 4 }
 => {:a=>1, :b=>2, :c=>4} 
2.0.0-p247 :013 > x.delete_if { |k,v| v % 2 == 0 }
 => {:a=>1} 
2.0.0-p247 :014 > x
 => {:a=>1} 


65.


counts = Hash.new(0) creamos un vector vacío pero que puede contener
 a parte de valores, punteros hacia esos valores. Pero en el
 counts = {} se crea un vector vacío, por lo que en este caso no hay
 diferencia.



66. 

 ["hello", "world", "hello", "LPP"]