My current favorite language~

1. APL – A Programming Language
By Bryan Wilson

2. //TODO - Header
• Short History
• Brief APL Rundown
• APL Details and Tools
• Syntax
– Data, Structures, Classes
– Functions, Operands
– System Variables, Functions
• Expanding APL

3. 30 Second History
• This language is crazy
• History sheds light on why

4. Enter Kenneth E. Iverson
Profession: Mathematics
“5 is greater than 1. Look”

5. His Notation
Relic found in ancient Mayan ruins.

6. A Pointless Language
• Entirely dynamic, highly abstract
• Largely interpreted (line by line execution)
• “Keywords” are symbols
• Tacit programming
• Short programs, probably about 1 line
• Write-only language

7. How the magic happens
• Right to left evaluation, except for parens
5 + 5
10
5 x 5
25
5 × 5 + 5
50
(5 × 5) + 5
30

8. Time to get crazy
• Types of data are largely done for you
1 2 3 + 5
6 7 8
¼9
1 2 3 4 5 6 7 8 9
2 4 ½¼9
1 2 3 4 5 6 7
8 9 1 2 3 4 5

9. Stop. Demotime.

10. Boring APL stuff
• Specifications
– ISO (International Standards Organization
– APL2, by IBM
• Interpreted
– Thus, Interpreters
• APL+
• APLX
• Dyalog APL
• VisualAPL

11. Interpreters
• Use workspaces, and have unique specs
– Workspace
– System Variables
– System Functions
• Modes
– Calculator mode
– Definition mode

12. Simple Data
• A number
– 24595
– Can be decimal or negative
• A character
– ‘s’
– Wrapped in single quotes
– ‘Use two ‘’ to escape the ‘’ ‘

13. Data Structures
• May have data, has dimensions
• Data does not have dimensions
• Struct – 1 item, no dimensions
• Vector- 1d list of items
• Matrix -2D..nD list of items
• Item can be character, number or structure
• Data structures can have mixed data, or nested

14. Data and structure syntax
• To store a variable
[name] „ [variable]
• Names can start with a letter and NOTHING
else
• Names can have numbers and some symbols
• Don’t duplicate names

15. Functions
• Types
– 0 arguments (niladic)
– 1 argument (monadic)
• Everything to the right
– 2 arguments (dyadic)
• Everything to the right
• First item to the left
• Can return data/data structure
• Bucket brigade
• Can be named like data
• One symbol, 1-2 functions, depending on arguments

16. Operations
• Modify the function of…functions.
– How functions are applied to data
• In addition to 0-2 arguments, can take 1-2
operands
• Functions can be operands
• Can also be named like functions

17. Classes
• Logical grouping of data and functions
„ŒNEW CLASSNAME
[classname].[function/property]
• Can have constructors.
• Some interpreters let you use external classes
– .NET

18. Alienspeak
• Arithmetic
+, -, ×, ÷, ⌈, ⌊, |
• Algebraic
⍳ , ? , * , ⍟, ○, ! , ⌹
• Comparative
<, ≤, =, ≥, >, ≠, ≡, ∊, ⍳, ⍷
• Logical
~, ∨, ^, ⍱, ⍲
• Manipulative
⍴, ≡, , , ∊, ~, ⌽, ⍉, ↑, ↓, ⊂, ⊃

19. Continued Mathyspeak
• Sorting
⍋, ⍒, ⊤, ⊥
• Miscellaneous
⎕, ⍞, ⋄, ⍕, ⍝, ⍎, ⌷, ⌻,¯
• Operators
/, , ., ∘. , ¨, [ ]

20. Defining your own functions
• It can be done! Watch!

21. System Variables and Functions
• Variables
– Easy to pick out, they start with Œ
– Change depending on interpreter
• Functions
– Start with a )
– Also change depending on interpreter

22. Can’t cover everything!
• Can you have threads?
– Yes. Some interpreters.
• Can you have labels?
– In function and operation definitions.
– This includes if/else and try/catch blocks
• Where can I learn more?
– Classes quoted at ~$2000 per day per person

23. The future is J
• APL transformed to be easier to read
quicksort=: (($:@(<#[), (=#[), $:@(>#[)) ({~ ?@#))
^: (1<#)

24. Summary
• Simply put:
– Dynamic
– Abstract
– Powerful
– Awesome

25. Questions for YOU
1. ⍳9 Returns what?
1 2 3 4 5 6 7 8 9
2. What does an operator in APL do?
Changes how a function is applied to data
3. To create a 3 dimensional array:
(1 2 3) ⍴ (5 4)

26. Questions for me?
There are three things a man must do
before his life is done
write two lines in APL,
and make the damn thing run