Crystal lang TCS presentation

argv.cr

# Demo of command line arguments
# ARGV[0]: First command line argument
# (not the executable name)
# ARGV is an array of strings
puts "Number of command line arguments: #{ARGV.size}"
ARGV.each_with_index {|arg, i| puts "Argument #{i}: #{arg}"}

# The executable name is available as PROGRAM_NAME
puts "Executable name: #{PROGRAM_NAME}"

def.cr

def sa(name : String) : Int32
    3
end

def foo(x, y : Int32 = 1, z : Int64 = 2)
    x + y + z
end

def foo(x : T)
end
foo(3) # x = 3, T = Int32

enumerable-functions.cr

strs = {"peach", "apple", "pear", "plum"}

puts strs.index("pear")
puts strs.includes?("grape")
puts strs.any? { |v| v.starts_with? "p" }
puts strs.all? { |v| v.starts_with? "p" }
puts strs.select { |v| v.includes? "e" }
puts strs.map { |v| v.upcase }

fact.cr

def fact(n : Int) : Int
   if n == 0
       return 1
   end
   return n * fact(n - 1)
end

puts fact 7 # => 5040

greeter.cr

class Greeter
   def initialize(name : String)
       @name = name
   end
 
   def salute
       puts "Hello #{@name}!"
   end
end

g = new Greeter("World")
g.salute # => Hello World!

time-formatting.cr

puts Time.parse("2012-11-01 22:08:12", "%F %T")

puts Time.parse("Fri Oct 31 23:00:24 2014", "%c")

puts Time.parse("20150624", "%Y%m%d")