diff options
Diffstat (limited to 'crystal.html.markdown')
| -rw-r--r-- | crystal.html.markdown | 70 |
1 files changed, 40 insertions, 30 deletions
diff --git a/crystal.html.markdown b/crystal.html.markdown index ae027a8d..d32712ce 100644 --- a/crystal.html.markdown +++ b/crystal.html.markdown @@ -4,6 +4,7 @@ filename: learncrystal.cr contributors: - ["Vitalii Elenhaupt", "http://veelenga.com"] - ["Arnaud Fernandés", "https://github.com/TechMagister/"] + - ["Valentin Baca", "https://github.com/valbaca/"] --- @@ -64,24 +65,25 @@ true.class #=> Bool 1.5e10.class #=> Float64 1.5e-7.class #=> Float64 -# Chars +# Chars use 'a' pair of single quotes 'a'.class #=> Char -# Octal codepoint -'\101' #=> 'A' : Char +# Chars are 32-bit unicode +'あ' #=> 'あ' : Char # Unicode codepoint '\u0041' #=> 'A' : Char -# Strings +# Strings use a "pair" of double quotes "s".class #=> String # Strings are immutable s = "hello, " #=> "hello, " : String s.object_id #=> 134667712 : UInt64 -s += "Crystal" #=> "hello, Crystal" : String +s += "Crystal" +s #=> "hello, Crystal" : String s.object_id #=> 142528472 : UInt64 # Supports interpolation @@ -89,7 +91,8 @@ s.object_id #=> 142528472 : UInt64 # Multiline string "This is - multiline string" + multiline string" #=> "This is\n multiline string" + # String with double quotes %(hello "world") #=> "hello \"world\"" @@ -110,7 +113,7 @@ sentence == "question?" #=> false : Bool # Arrays [1, 2, 3].class #=> Array(Int32) -[1, "hello", 'x'].class #=> Array(Int32 | String | Char) +[1, "hello", 'x'].class #=> Array(Char | Int32 | String) # Empty arrays should specify a type [] # Syntax error: for empty arrays use '[] of ElementType' @@ -154,24 +157,24 @@ array.includes? 3 #=> true # There is a special array syntax with other types too, as long as # they define a .new and a #<< method -set = Set{1, 2, 3} #=> [1, 2, 3] +set = Set{1, 2, 3} #=> Set{1, 2, 3} set.class #=> Set(Int32) # The above is equivalent to -set = Set(typeof(1, 2, 3)).new -set << 1 -set << 2 -set << 3 +set = Set(typeof(1, 2, 3)).new #=> Set{} : Set(Int32) +set << 1 #=> Set{1} : Set(Int32) +set << 2 #=> Set{1, 2} : Set(Int32) +set << 3 #=> Set{1, 2, 3} : Set(Int32) # Hashes {1 => 2, 3 => 4}.class #=> Hash(Int32, Int32) -{1 => 2, 'a' => 3}.class #=> Hash(Int32 | Char, Int32) +{1 => 2, 'a' => 3}.class #=> Hash(Char| Int32, Int32) -# Empty hashes should specify a type -{} # Syntax error -{} of Int32 => Int32 # {} -Hash(Int32, Int32).new # {} +# Empty hashes must specify a type +{} # Syntax Error: for empty hashes use '{} of KeyType => ValueType' +{} of Int32 => Int32 # {} : Hash(Int32, Int32) +Hash(Int32, Int32).new # {} : Hash(Int32, Int32) # Hashes can be quickly looked up by key hash = {"color" => "green", "number" => 5} @@ -179,6 +182,9 @@ hash["color"] #=> "green" hash["no_such_key"] #=> Missing hash key: "no_such_key" (KeyError) hash["no_such_key"]? #=> nil +# The type of the returned value is based on all key types +hash["number"] #=> 5 : (Int32 | String) + # Check existence of keys hash hash.has_key? "color" #=> true @@ -220,7 +226,7 @@ Range.new(1, 10).class #=> Range(Int32, Int32) # Access tuple's value by its index tuple = {:key1, :key2} tuple[1] #=> :key2 -tuple[2] #=> syntax error : Index out of bound +tuple[2] #=> Error: index out of bounds for Tuple(Symbol, Symbol) (2 not in -2..1) # Can be expanded into multiple variables a, b, c = {:a, 'b', "c"} @@ -246,7 +252,7 @@ elsif false "else-if, optional" else "else, also optional" -end +end puts "if as a suffix" if true @@ -314,7 +320,7 @@ if a < 3 else a = true end -typeof a #=> (Bool | String) +typeof(a) #=> (Bool | String) if a && b # here both a and b are guaranteed not to be Nil @@ -388,15 +394,19 @@ dinner #=> "quesadilla" 5.even? # false 5.odd? # true -# And if a method ends with an exclamation mark, it does something destructive -# like mutate the receiver. Some methods have a ! version to make a change, and +# Also by convention, if a method ends with an exclamation mark, it does +# something destructive like mutate the receiver. +# Some methods have a ! version to make a change, and # a non-! version to just return a new changed version -company_name = "Dunder Mifflin" -company_name.gsub "Dunder", "Donald" #=> "Donald Mifflin" -company_name #=> "Dunder Mifflin" -company_name.gsub! "Dunder", "Donald" -company_name #=> "Donald Mifflin" +fruits = ["grapes", "apples", "bananas"] +fruits.sort #=> ["apples", "bananas", "grapes"] +fruits #=> ["grapes", "apples", "bananas"] +fruits.sort! #=> ["apples", "bananas", "grapes"] +fruits #=> ["apples", "bananas", "grapes"] +# However, some mutating methods do not end in ! +fruits.shift #=> "apples" +fruits #=> ["bananas", "grapes"] # Define a class with the class keyword class Human @@ -404,7 +414,7 @@ class Human # A class variable. It is shared by all instances of this class. @@species = "H. sapiens" - # type of name is String + # An instance variable. Type of name is String @name : String # Basic initializer @@ -469,9 +479,9 @@ class TestClass end # Variables that start with a capital letter are constants Var = "I'm a constant" -Var = "can't be updated" # Already initialized constant Var +Var = "can't be updated" # Error: already initialized constant Var -# Class is also an object in crystal. So class can have instance variables. +# Class is also an object in Crystal. So a class can have instance variables. # Class variable is shared among the class and all of its descendants. # base class |