A gentle introduction to types

- What are types?
- Why types?
- Dynamic v Static typing
- Gradual typing
- Examples
- Advantages

Transcript

1. TYPES
2. - - -
3. • • • • AGENDA
5. CLASS OF VALUES
6. CLASS OF VALUES OPERATIONS
7. CLASS OF VALUES OPERATIONS Set of Rules for a variable
9. HUMANS
10. HUMANS make MISTAKES!!!!
11. COMPUTERS
12. COMPUTERS can REPEAT!!!!!!!!!!!!
13. COMPUTERS HUMANS
19. TYPE SYSTEMS.
21. TYPE SYSTEMS
22. TYPE SYSTEMS SOURCE
23. TYPE SYSTEMS SOURCE
24. TYPE SYSTEMS SOURCE
25. TYPE SYSTEMS SOURCE TypeError: unsupported operand type(s) for +: 'int' and 'str'
26. TYPE SYSTEMS ?
27. CLASS OF VALUES OPERATIONS
28. VAR VAR VAR VAR VAR VAR
29. VAR VAR VAR VAR VAR VAR
30. VAR VAR VAR VAR VAR VAR
31. VAR VAR VAR VAR VAR VAR VAR
32. VAR VAR VAR VAR VAR VAR VAR
34. TYPES STATIC TYPES DYNAMIC
35. TYPES STATIC TYPES DYNAMIC WRONG!!!1
36. RUNTIME
37. ??? STATIC TYPES ??? DYNAMIC TYPES
38. COMPILE TIME STATIC TYPES RUN TIME DYNAMIC TYPES
39. >>> people = [] PYTHON
40. >>> people = [] >>> people.append({ “name”: “Foo”, “age”: “26” }) >>> people.append({ “name”: “Bar” “age”: 28 }) PYTHON
41. >>> people = [] >>> people.append({ “name”: “Foo”, “age”: “26” }) >>> people.append({ “name”: “Bar” “age”: 28 }) >>> [ person[“age”] + 2 for person in people ] PYTHON
42. >>> people = [] >>> people.append({ “name”: “Foo”, “age”: “26” }) >>> people.append({ “name”: “Bar” “age”: 28 }) >>> [ person[“age”] + 2 for person in people ] ... TypeError: cannot concatenate 'str' and 'int' objects PYTHON
43. >>> people = [] >>> people.append({ “name”: “Foo”, “age”: “26” }) >>> people.append({ “name”: “Bar” “age”: 28 }) >>> [ person[“age”] + 2 for person in people ] ... TypeError: cannot concatenate 'str' and 'int' objects PYTHON RUNTIME
44. C# class Person { public string Name {get; set;} public int Age {get; set;} }
45. var people = new List<Person>(); C# class Person { public string Name {get; set;} public int Age {get; set;} }
46. var people = new List<Person>(); people.Add(new Person { Name = “Foo”, Age = “26” }); people.Add(new Person { Name = “Bar”, Age = 28 }); C# class Person { public string Name {get; set;} public int Age {get; set;} }
47. var people = new List<Person>(); people.Add(new Person { Name = “Foo”, Age = “26” }); people.Add(new Person { Name = “Bar”, Age = 28 }); people.Select(p => p.Age + 2); C# class Person { public string Name {get; set;} public int Age {get; set;} }
48. var people = new List<Person>(); people.Add(new Person { Name = “Foo”, Age = “26” }); people.Add(new Person { Name = “Bar”, Age = 28 }); people.Select(p => p.Age + 2); C# class Person { public string Name {get; set;} public int Age {get; set;} } Cannot implicitly convert type 'string' to 'int'
49. var people = new List<Person>(); people.Add(new Person { Name = “Foo”, Age = “26” }); people.Add(new Person { Name = “Bar”, Age = 28 }); people.Select(p => p.Age + 2); C# class Person { public string Name {get; set;} public int Age {get; set;} } Cannot implicitly convert type 'string' to 'int' COMPILE TIME
50. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name PYTHON string GetGreeting(string name) { if (name.Length > 5) return “Helloooo “ + name } C#
51. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name PYTHON
52. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name get_greeting(“Jon Snow”).upper() PYTHON
53. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name get_greeting(“Jon Snow”).upper() get_greeting(“Jon”).upper() PYTHON
54. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name get_greeting(“Jon Snow”).upper() get_greeting(“Jon”).upper() PYTHON AttributeError: 'NoneType' object has no attribute 'upper'
55. def get_greeting(name): if len(name) > 5: return “Helloooo “ + name get_greeting(“Jon Snow”).upper() get_greeting(“Jon”).upper() PYTHON AttributeError: 'NoneType' object has no attribute 'upper' RUNTIME
56. string GetGreeting(string name) { if (name.Length > 5) return “Helloooo “ + name } C#
57. string GetGreeting(string name) { if (name.Length > 5) return “Helloooo “ + name } C# else?
58. string GetGreeting(string name) { if (name.Length > 5) return “Helloooo “ + name } C# else? Not all code paths return a value
59. string GetGreeting(string name) { if (name.Length > 5) return “Helloooo “ + name } C# else? Not all code paths return a value COMPILE TIME
60. DYNAMIC TYPING STATIC TYPING
61. DYNAMIC TYPING STATIC TYPING
62. DYNAMIC TYPING STATIC TYPING ANY GOOD?
63. DYNAMIC TYPING • • • • •
64. DYNAMIC TYPING STATIC TYPING ANY BAD?
65. STATIC TYPING • • • •
66. DYNAMIC TYPING STATIC TYPING
67. DYNAMIC TYPING STATIC TYPING
68. DYNAMIC TYPING STATIC TYPING
69. GRADUAL TYPING DYNAMIC TYPING STATIC TYPING
71. GRADUAL TYPING
72. GRADUAL TYPING DYNAMIC TYPING STATIC TYPING
73. GRADUAL TYPING DYNAMIC TYPING STATIC TYPING Compile Time Rigidity Runtime Fluidity
74. GRADUAL TYPING FRAMEWORKS
77. GRADUAL TYPING POWERS • • • • •
79. • • • • • AGENDA
80. FIN.