ktanaka101

test

ktanaka101

3.0 / 2.0
3.0 // 2.0

3.0 / 2
3.0 // 2

3 / 2
3 // 2

3 / 2.0

ktanaka101

if true
  a = 10
else
  b = 20
end

p a #=> 10
p b #=> nil

ktanaka101

# crystal
str1 = "
  if true
    10
  else
    20
  end
"

str2 = <<-STR

ktanaka101

# crystal
a = <<-INPUT
  10
INPUT #=> syntax ok

b = {
  <<-INPUT
    10
  INPUT, 10
} #=> syntax error

ktanaka101

# crystal
## string is immutable

str = ""
str.object_id #=> 94763530681144_u64

str += "abc"

str.object_id #=> 94494250273768_u64

ktanaka101

alias A = Int32 -> Int32

A.new do |x|
  return x
end #=> Proc(Int32, Int32)

ktanaka101

# crystal

def a(*args : Int32)
  args
end
a(1, 2) #=> {1, 2}
a(1) #=> {1}

def b(a, b)
  a + b

ktanaka101

# crystal
arr = [1, 2, 3, 4, 5]

arr[1..-1]  #=> [2, 3, 4, 5]
arr[1...-1] #=> [2, 3, 4]
arr[-2..-1] #=> [4, 5]
(1..2).includes?(2) #=> true
(1...2).includes?(2) #=> false

ktanaka101

# crystal
{"a" => 1, "b" => 2} #=> {"a" => 1, "b" => 2} : Hash(String, Int32)
a = {"a": 1, "b": 2} #=> {a: 1, b: 2} : NamedTuple(a: Int32, b: Int32)

{"a" => 1, "b": 2} #=> {"a" => 1, "b" => 2}
{"a": 1, "b" => 2} #=> Syntax error in :6: space not allowed between named argument name and ':'