Ruby is Magic: Flip-Flop

After a very long break we finally did another Ruby is Magic at Cologne.rb. This time we went with arguably the most absurd feature in Ruby: The flip-flop operator. As usual the slides are in German and don't work well without the live performance ;-)

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Transcript

1. Ruby cologne.rb Nein! Doch! Ohh
2. Previously on Ruby is Magic (viele) Absurditäten und (etwas) Nützliches Verrückter Syntax Inkonsistenzen Kuriositäten
3. Einflüsse auf Ruby Smalltalk Perl awk
4. $! $_ $1, $2, $3 BEGIN END .. ...
5. Peak Ruby is Magic Today
6. Nein! Doch! Ohh!
8. $! $_ $1, $2, $3 BEGIN END .. ...
9. $! $_ $1, $2, $3 BEGIN END .. ...
10. .. ... 1..5 1...5 Range
11. SKEPTICAL PINKIE PIE SKEPTICAL PINKIE PIE IS SKEPTICAL IS SKEPTICAL
12. Fun Fact™ if (x == 5)..(x == 10) puts x end Not a Range literal!
13. IS EVEN MOAR SKEPTICAL IS EVEN MOAR SKEPTICAL SKEPTICAL PINKIE PIE SKEPTICAL PINKIE PIE
14. Flip-Flop
15. Flip-Flop In scalar context, ".." returns a boolean value. The operator is bistable, like a flip-flop, and emulates the line-range (comma) operator of sed, awk, and various editors. Each ".." operator maintains its own boolean state, even across calls to a subroutine that contains it. It is false as long as its left operand is false. Once the left operand is true, the range operator stays true until the right operand is true, AFTER which the range operator becomes false again. It doesn't become false till the next time the range operator is evaluated. It can test the right operand and become false on the same evaluation it became true (as in awk), but it still returns true once. If you don't want it to test the right operand until the next evaluation, as in sed, just use three dots ("...") instead of two. In all other regards, "..." behaves just like ".." does. The right operand is not evaluated while the operator is in the "false" state, and the left operand is not evaluated while the operator is in the "true" state. The precedence is a little lower than || and &&. The value returned is either the empty string for false, or a sequence number (beginning with 1) for true. The sequence number is reset for each range encountered. The final sequence number in a range has the string "E0" appended to it, which doesn't affect its numeric value, but gives you something to search for if you want to exclude the endpoint. You can exclude the beginning point by waiting for the sequence number to be greater than 1. If either operand of scalar ".." is a constant expression, that operand is considered true if it is equal (==) to the current input line number (the $. variable).
16. Quelle: http:/ /perldoc.perl.org/perlop.html#Range-Operators Flip-Flop In scalar context, ".." returns a boolean value. The operator is bistable, like a flip-flop, and emulates the line-range (comma) operator of sed, awk, and various editors. Each ".." operator maintains its own boolean state, even across calls to a subroutine that contains it. It is false as long as its left operand is false. Once the left operand is true, the range operator stays true until the right operand is true, AFTER which the range operator becomes false again. It doesn't become false till the next time the range operator is evaluated. It can test the right operand and become false on the same evaluation it became true (as in awk), but it still returns true once. If you don't want it to test the right operand until the next evaluation, as in sed, just use three dots ("...") instead of two. In all other regards, "..." behaves just like ".." does. The right operand is not evaluated while the operator is in the "false" state, and the left operand is not evaluated while the operator is in the "true" state. The precedence is a little lower than || and &&. The value returned is either the empty string for false, or a sequence number (beginning with 1) for true. The sequence number is reset for each range encountered. The final sequence number in a range has the string "E0" appended to it, which doesn't affect its numeric value, but gives you something to search for if you want to exclude the endpoint. You can exclude the beginning point by waiting for the sequence number to be greater than 1. If either operand of scalar ".." is a constant expression, that operand is considered true if it is equal (==) to the current input line number (the $. variable). Perl!
17. Ruby Documentation?
19. DON’T KNOW IF REAL FEATURE DON’T KNOW IF REAL FEATURE OR JUST FORGOTTEN TO REMOVE OR JUST FORGOTTEN TO REMOVE
21. (1..5).each do |x| puts x if (x == 2)..(x == 4) end
22. (1..5).each do |x| puts x if (x == 2)..(x == 4) end => 2 3 4
23. (x == 2)..(x == 4) Input
24. x=1 (x == 2)..(x == 4) Input
25. x=1 false (x == 2)..(x == 4) Input
26. x=1 false false (x == 2)..(x == 4) Input
27. x=1 false false (x == 2)..(x == 4) if: false #=> Input
28. x=1 false false (x == 2)..(x == 4) x=2 true false if: false #=> if: true #=> 2 Input
29. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 false false if: false #=> if: true #=> 2 if: true #=> 3 Input
30. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 false false x=4 false true if: false #=> if: true #=> 2 if: true #=> 3 if: true #=> 4 Input
31. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 false false x=4 false true x=5 false false if: false #=> if: true #=> 2 if: true #=> 3 if: true #=> 4 if: false #=> Input
33. In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. Quelle: https://de.wikipedia.org/wiki/Flipflop
34. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State
35. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State !
36. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State ! " !
37. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State ! " " !
38. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State ! " " ! " !
39. x=1 false false (x == 2)..(x == 4) x=2 true false x=3 nil false x=4 nil true x=5 false false if: false if: true if: true if: true if: false Input flip-flop State ! " " ! " ! !
40. Der flip-flop evaluiert immer dann zu true, wenn er aufgeht oder offen war
41. LET’S USE IT THEN! LET’S USE IT THEN!
42. Fiij Buij
43. ★ Gebe die Zahl aus ★ Gebe 'Fizz' aus wenn Zahl durch 3 teilbar ★ Gebe 'Buzz' aus wenn Zahl durch 5 teilbar ★ Gebe 'FizzBuzz' aus wenn Zahl durch 3 und 5 teilbar
44. a=b=c = nil # Initialisierung! ! (1..100).each do |num| fizz = true unless (a = !a) .. (a = !a) buzz = true unless (b = !b) ... !((c = !c) .. (c = !c)) ! print_it(num, fizz, buzz) end
46. (a = !a)..(a = !a) a=… flip-flop State
47. (a = !a)..(a = !a) a=… flip-flop State nil
48. (a = !a)..(a = !a) a=… flip-flop State nil true
49. (a = !a)..(a = !a) a=… flip-flop State nil true false
50. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " !
51. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " ! false nil true if: true " !
52. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " ! false nil true if: true " ! true false nil if: false !
53. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " ! false nil true if: true " ! true false nil if: false ! false true false if: true " !
54. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " ! false nil true if: true " ! true false nil if: false ! false true false if: true " ! false nil true if: true " !
55. (a = !a)..(a = !a) a=… flip-flop State nil true false if: true " ! false nil true if: true " ! true false nil if: false ! false true false if: true " ! false nil true if: true " ! true false nil if: false !
56. a=b=c = nil # Initialisierung! ! (1..100).each do |num| fizz = true unless (a = !a) .. (a = !a) ! print_it(num, fizz, buzz) end ✔ buzz = true unless (b = !b) ... !((c = !c) .. (c = !c))
57. buzz = true unless (b = !b) ... !((c = !c) .. (c = !c))
58. buzz = true unless (b = !b) ... !((c = !c) .. (c = !c)) (a = !a) .. (a = !a) unless fizz_flipflop
59. (b = !b)...(fizz_flipflop) b=… flip-flop State
60. (b = !b)...(fizz_flipflop) b=… flip-flop State nil
61. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true
62. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil
63. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " !
64. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " ! true nil false if: true "
65. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " ! true nil false true nil false if: true " if: true "
66. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " ! true nil false true nil false if: true " true nil true if: true " ! if: true "
67. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " ! true nil false true nil false if: true " true nil true true false nil if: true " ! if: true " if: false !
68. (b = !b)...(fizz_flipflop) b=… flip-flop State nil true nil if: true " ! true nil false true nil false if: true " true nil true true false nil if: true " ! false true nil if: true " if: false ! if: true " !
69. a=b=c = nil # Initialisierung! ! (1..100).each do |num| fizz = true unless (a = !a) .. (a = !a) buzz = true unless (b = !b) ... !((c = !c) .. (c = !c)) ! print_it(num, fizz, buzz) end ✔
70. a=b=c = nil # Initialisierung! ! (1..100).each do |num| fizz = true unless (a = !a) .. (a = !a) buzz = true unless (b = !b) ... !((c = !c) .. (c = !c)) ! print_it(num, fizz, buzz) end ✔ ✔
71. 1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 … a=b=c = nil # Initialisierung! ! (1..100).each do |num| fizz = true unless (a = !a) .. (a = !a) buzz = true unless (b = !b) ... !((c = !c) .. (c = !c)) ! print_it(num, fizz, buzz) end
72. a=b=c=(1..100).each do |num| print num, ?\r, ("Fizz" unless (a = !a) .. (a = !a)), ("Buzz" unless (b = !b) ... !((c = !c) .. (c = !c))), ?\n end
73. ★ Sehr viel Komplexität ★ Extrem unbekannt ★ Schlecht zu debuggen ★ Für awk/sed Funktionalität „sinnvoll“ d Finger weg!!!
74. Some More Things …
76. ruby.town @ruby_town Ruby-Assemblies-on- Chaos-Communication-Congress-and- Chaos-Communication-Camp
77. Harassment, Misogyny and Hatred against women and minorities in IT and Open Source Harassment, Misogyny and Hatred against women and minorities in IT and Open Source
78. https://modelviewculture.com/support Go to:
79. Thanks! Dirk Breuer / @railsbros_dirk Sebastian Cohnen / @tisba http://geekstammtisch.de QaA “My Little Pony” © Hasbro Studios and DHX Media Vancouver ✗