examples

crystal/classes.md

@@ -79,3 +79,15 @@ To be able to compare two objects based on their attributes only we can used the
 * [Object](https://crystal-lang.org/api/Object.html)
 
 ![](examples/classes/compare_objects.cr)
+
+## Singleton using class properties
+{id: singleton-using-class-properties}
+{i: class_property}
+
+![](examples/classes/singleton_using_class_properties.cr)
+
+## Singleton using class properties with default values
+{id: singleton-using-class-properties-with-defaults}
+{i: class_property}
+
+![](examples/classes/singleton_using_class_properties_with_defaults.cr)

crystal/examples/classes/singleton_using_class_properties.cr

@@ -0,0 +1,13 @@
+class Options
+    class_property repetition : Int32|Nil
+    class_property url = String
+    class_property verbose = Bool
+end
+
+puts Options.repetition
+Options.repetition = 3
+puts Options.repetition
+if ! Options.repetition.nil?
+    puts Options.repetition + 1
+end
+

crystal/examples/classes/singleton_using_class_properties_with_defaults.cr

@@ -0,0 +1,9 @@
+class Options
+    class_property repetition = 0
+    class_property url = ""
+    class_property verbose = false
+end
+puts Options.repetition
+Options.repetition = 3
+puts Options.repetition
+puts Options.repetition + 1

crystal/examples/functions/array_overload.cr

@@ -0,0 +1,10 @@
+def f(x, y)
+    return x + y
+end
+def f(args : Array(Int32))
+    return f(args[0], args[1])
+end
+puts  f(2, 3)
+values = [3, 4]
+puts values
+puts f(values)

crystal/examples/functions/manually_separate.cr

@@ -0,0 +1,8 @@
+def f(x, y)
+    return x + y
+end
+puts  f(2, 3)
+values = [3, 4]
+puts values
+
+puts f(values[0], values[1])

crystal/examples/functions/pass_array_instead_of_individual_values.cr

@@ -0,0 +1,11 @@
+def f(x, y)
+    return x + y
+end
+puts  f(2, 3)
+values = [3, 4]
+puts values
+
+puts f(values[0], values[1])
+
+# puts f(values)
+# Error: wrong number of arguments for 'f' (given 1, expected 2)

crystal/examples/functions/tuple_from.cr

@@ -0,0 +1,8 @@
+def f(x, y)
+    return x + y
+end
+puts  f(2, 3)
+values = [3, 4]
+puts values
+
+puts f(*{Int32, Int32}.from(values))

crystal/examples/try.cr

@@ -1,56 +1,57 @@
 
-person = {
-    "name" => "Foo Bar",
-    "number" => 42,
-}
-p! person
-puts typeof(person) # Hash(String, Int32 | String)
-
-joe = {} of String => Int32 | String
-joe["name"] = "Joe"
-joe["number"] = 23
-# joe["float"] = 2.3
-# compile time error
-# Error: no overload matches 'Hash(String, Int32 | String)#[]=' with types String, Float64
-puts typeof(joe)
-
-
-#alias Some = {} of String => Int32 | String
-
-numbers = [] of Int32
-numbers.push(23)
-# numbers.push("text")
-# Error: no overload matches 'Array(Int32)#push' with type String
-# numbers.push(nil)
-# Error: no overload matches 'Array(Int32)#push' with type Nil
-puts typeof(numbers)
-
-alias Int32orNil = Int32|Nil
-# nilnum = [] of Int32 | Nil
-nilnum = [] of Int32orNil
-nilnum.push(23)
-nilnum.push(nil)
-puts typeof(nilnum)
-#num = Int32
-#num = 23
-#num = nil
-
-# class Person
-#     name: {type: String}
-#     number: {type: Int32}
-# end
-
-#alias Person = {name: String, number: Int32}
-alias Person = NamedTuple(name: String, number: Int32)
-
-people = [] of Person
-puts typeof(people)
-people.push({
-    "name": "Foo Bar",
-    "number": 42
-})
-
-puts people[0]["name"]
-# people[0]["name"] = "New Name"
-# Error: undefined method '[]=' for NamedTuple(name: String, number: Int32)
 
+
+# person = {
+#     "name" => "Foo Bar",
+#     "number" => 42,
+# }
+# p! person
+# puts typeof(person) # Hash(String, Int32 | String)
+
+# joe = {} of String => Int32 | String
+# joe["name"] = "Joe"
+# joe["number"] = 23
+# # joe["float"] = 2.3
+# # compile time error
+# # Error: no overload matches 'Hash(String, Int32 | String)#[]=' with types String, Float64
+# puts typeof(joe)
+
+
+# #alias Some = {} of String => Int32 | String
+
+# numbers = [] of Int32
+# numbers.push(23)
+# # numbers.push("text")
+# # Error: no overload matches 'Array(Int32)#push' with type String
+# # numbers.push(nil)
+# # Error: no overload matches 'Array(Int32)#push' with type Nil
+# puts typeof(numbers)
+
+# alias Int32orNil = Int32|Nil
+# # nilnum = [] of Int32 | Nil
+# nilnum = [] of Int32orNil
+# nilnum.push(23)
+# nilnum.push(nil)
+# puts typeof(nilnum)
+# #num = Int32
+# #num = 23
+# #num = nil
+
+# # class Person
+# #     name: {type: String}
+# #     number: {type: Int32}
+# # end
+
+# #alias Person = {name: String, number: Int32}
+# alias Person = NamedTuple(name: String, number: Int32)
+
+# people = [] of Person
+# puts typeof(people)
+# people.push({
+#     "name": "Foo Bar",
+#     "number": 42
+# })
+
+# puts people[0]["name"]
+# # people[0]["name"] = "New Name"
+# # Error: undefined method '[]=' for NamedTuple(name: String, number: Int32)

crystal/functions.md

@@ -22,4 +22,28 @@
 
 * Type definition for parameters
 * Return Type definition
-* Multi-dispatch functions with same name but different signature
+* Multi-dispatch functions with same name but different signature
+
+## Wrong number of arguments
+{id: wrong-number-of-arguments}
+
+* We have a function that expect two integers. Can we instead pass an array of two integers?
+* Normally no, but there are at least 3 solutions
+
+![](examples/functions/pass_array_instead_of_individual_values.cr)
+
+## Manually separate
+{id: manually-separate}
+
+![](examples/functions/manually_separate.cr)
+
+## Tuple from
+{id: tuple-from}
+
+![](examples/functions/tuple_from.cr)
+
+
+## Array overload
+{id: array-overload}
+
+![](examples/functions/array_overload.cr)