The document discusses the concept of 'eager design' in software development, emphasizing methods such as jumping to the relevant problem, replacing primitive types with structured types, and maintaining immutability. It features various examples and functions related to scheduling in a chess app, showcasing how to handle player matching and rounds efficiently. The philosophy promotes creativity through limited information and intelligent constraints to enhance the design process.

1. EagerDesign
by @_md
♞
marcelloduarte
Introducing

2. marcelloduarte
@_md
#EagerDesign

3. agileislazy
@_md#EagerDesign

4. "Makethecommitmentatthelast
responsiblemoment"
Preston Smith
decide later

5. softwareisaboutpeople
@_md#EagerDesign

6. ageofexcess
@_md#EagerDesign

7. subtraction
@_md#EagerDesign

8. subtraction
@_md#EagerDesign

9. lawsofsubtraction
@_md

10. lawsofsubtraction
whatisn’ttherecanoftentrumpwhatis.thesimplest
rulescreatethemosteffectiveexperience.limiting
informationengagesimagination.creativitythrives
underintelligentconstraints.breakistheimportant
partofbreakthrough.doingsomethingisn’talways
betterthandoingnothing.
Matthew E. May

12. EagerDesign
how
♞
Jumptotheproblemworthsolving
Eagerlyreplaceprimitiveswithtypes
Compose[thedomainalgebra] inside-out
Avoidmutablestate
#1
#2
#3
#4
@_md#EagerDesign

13. outside-in
♞

14. outside-in
unittest code
refactor
acceptance
ui/controller/views
orm,libs,domainobjects
frameworkstuff(forms…)
model/view/controller

15. events
outside-in
UI
Domain
core
Application
Infrastructure
mobileUI
port/adapter
port/adapterDB
https://pbs.twimg.com/media/CHyUAukWgAA5iYS.jpg
reads
writes

16. therightoutside
http://bit.ly/modellingbyexample
http://bit.ly/whencucumbersgobad
@_md#EagerDesign

17. {
outside-in
slow
misleading
complex
restrictscomposability

18. when?

19. EagerDesign
when
done
trivial
done
nottrivial
notdone
noidea
[based on Cynefin, Snowden 03]
@_md#EagerDesign

20. EagerDesign
when
done
trivial
done
nottrivial
notdone
noidea
[based on Cynefin, Snowden 03]
Outside-in
@_md#EagerDesign

21. EagerDesign
when
done
trivial
done
nottrivial
notdone
noidea
[based on Cynefin, Snowden 03]
EagerDesign
Outside-in
@_md#EagerDesign

22. EagerDesign
when
done
trivial
done
nottrivial
notdone
noidea
[based on Cynefin, Snowden 03]
EagerDesign
Outside-in
¯_(ツ)_/¯
@_md#EagerDesign

23. Example

25. {
chessapp
weaddplayers
itgeneratestheschedule
wecanentertheresults
wecanseetheranking
TRIVIAL
TRIVIAL
TRIVIAL
EagerDesign
@_md

26. {
domainrules
playerswillplaywitheveryotherplayer
playerscan'tplaytwiceinthesameround
everyplayermustplayineveryround
playersmustplaytwicewithanotherplayer
@_md

27. HowdoIconvert
alistofthings
intoalistofuniquelists
ofuniquepairs?

28. Letmethink

29. a b c d e f g h
List of things

30. a b c d e f g h
List of things
Pairs
a b c d
h g f e

31. Pairs
a b c d
h g f e

32. Shift to the right
a b c d
h g f ee

33. We haz roundz! :o)
a b c d
h g f ee

34. r1 r2 r3 r4
r5 r6 r7
+ r1 r2 r3 r4
r5 r6 r7
inverse
( )

36. r1 r2 r3 r4
r5 r6 r7 r8
r9 r10 r11 r12
r13 r14
shuffle
( )

38. lawsofsubtraction
whatisn’ttherecanoftentrumpwhatis.thesimplest
rulescreatethemosteffectiveexperience.limiting
informationengagesimagination.creativitythrives
underintelligentconstraints.breakistheimportant
partofbreakthrough.doingsomethingisn’talways
betterthandoingnothing.
Matthew E. May

39. #1Jumptotheproblemworthsolving
@_md#EagerDesign

40. http://github.com/MarcelloDuarte/phunkie

41. ImmList
a b c d e f g hhead
a b c d e f g htail
a b c d e f g hinit
a b c d e f g hlast

42. concat(
head($players),
last($players),
init(tail($players))

43. function shift(ImmList $players)
{
return concat(head($players),
last($players),
init(tail($players))
);
}

44. function shift(ImmList $players)
{
return concat(head($players),
last($players),
init(tail($players))
);
}

45. function round(ImmList $players)
{
$sides = $players->splitAt($players->length/2);
return $sides->_1->zip($sides->_2->reverse());
}

46. function rounds(ImmList $players)
{
}

47. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}

48. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}

49. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}

50. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}
#3Compose

51. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}
#4Avoidmutablestate

52. function rounds(ImmList $players, $rounds = [])
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}

53. function schedule(ImmList $players)
{
return concat(rounds($players),
inverse(rounds($players));
}

54. #2Eagerlyreplaceprimitiveswithtypes
@_md#EagerDesign

55. “Mymathbackgroundmademerealise
thateachobjectcouldhaveseveral
algebrasassociatedwithit,andthere
couldbefamiliesofthese,andthatthese
wouldbeveryveryuseful...

56. ...Imadeupaterm"genericity"for
dealingwithgenericbehavioursina
quasi-algebraicform...

57. ...Ididn'tlikethewaySimulaIorSimula
67didinheritance.SoIdecidedtoleave
outinheritanceasabuilt-infeatureuntilI
understooditbetter.”
AlanKay

58. http://bit.ly/meaning-­‐of-­‐oo

59. type Player = string;
type Players = ImmList<Player>;
type Match = Pair<Player,Player>
type Round = ImmList<Match>;
type Rounds = ImmList<Round>;
type Schedule = Rounds;

61. function shift(Players $players): Players
{
return concat(head($players),
last($players),
init(tail($players))
);
}

62. function round(Players $players): Round
{
$sides = $players->splitAt($players->length/2);
return $sides->_1->zip($sides->_2->reverse());
}

63. function rounds(Players $players, $rounds = [])
: Rounds
{
$rounds[] = round($players);
return count($rounds) < $players->length - 1 ?
rounds(shift($players), $rounds) :
ImmList(...$rounds);
}

64. function schedule(Players $players): Rounds
{
return concat(rounds($players),
inverse(rounds($players));
}

65. Composethedomainalgebra
inside-out
@_md#EagerDesign

66. namespace MdChessScheduleGeneration;
shift(Players $players): Players
round(Players $players): Round
rounds(Players $players): Rounds
schedule(Players $players): Schedule

67. ♞
Players => Schedule

68. Players => Rounds => Schedule
♞

69. Players => Round => Rounds => Schedule
♞

70. domainrulesaredefined
againsttypes
@_md#EagerDesign

71. {
domainrules
playerswillplaywitheveryotherplayer
playerscan'tplaytwiceinthesameround
everyplayermustplayineveryround
playersmustplaytwicewithanotherplayer
@_md

72. richdomainmodelvs
leandomainmodel

73. S
S
S
S
S
S
@_md#EagerDesign
richdomain

74. ImmutableState
ImmutableState
ImmutableState
B B
leandomain
Laws

75. InterpretingServicesAgency
Example
@_md#EagerDesign

76. def request
def decline
def amend
def accept
def done

77. def request(details:JobDetails): Job
def decline(ref:JobRef): Job
def amend(details:JobDetails): Job => Option[TimeSheet]
def accept(ref:JobRef): Job => Option[TimeSheet]
def done(ref:JobRef): TimeSheet => Remittance

78. trait JobService
{
def request(details:JobDetails): Job
def decline(ref:JobRef): Job
def amend(details:JobDetails):Job => Option[TimeSheet]
def accept(ref:JobRef): Job => Option[TimeSheet]
def done(ref:JobRef): TimeSheet => Remittance
}

79. trait JobService
{
def request(details:JobDetails): Job
def decline(ref:JobRef): Job
def amend(details:JobDetails):Job => Option[TimeSheet]
def accept(ref:JobRef): Job => Option[TimeSheet]
def done(ref:JobRef): TimeSheet => Remittance
}

80. f(a:A):M[B]
g(a:B):M[C]

81. f(a:A):M[B]
f(a) map g = M[M[C]]
g(a:B):M[C]

82. f(a:A):M[B]
join f(a) map g = M[C]
g(a:B):M[C]

83. f(a:A):M[B]
andThen
g(a:B):M[C]

84. request andThen
amend andThen
done

85. def execute(input:Input): Unit
path = input("path").getOrElse("specs")
loadSpecs(path) andThen
runSpecs andThen
presentResults

86. what’stheeagerpoint?
@_md#EagerDesign

88. merging2cells!!
@_md#EagerDesign

89. {
3cases
samevalue
differentvalue
righthandsideis
empty

90. if ($this->value == $another->value) {
return Pair(Cell(),
Cell($this->value + $another->value));
} elseif ($another->isEmpty()) {
return Pair(Cell(), Cell($this->value));
}
return Pair(Cell($this->value), Cell($another->value));

91. if ($this->value == $another->value) {
return Pair(Cell(),
Cell($this->value + $another->value));
} elseif ($another->isEmpty()) {
return Pair(Cell(), Cell($this->value));
}
return Pair(Cell($this->value), Cell($another->value));

92. if ($this->value == $another->value) {
return Pair(Cell(),
Cell($this->value + $another->value));
} elseif ($another->isEmpty()) {
return Pair(Cell(), Cell($this->value));
}
return Pair(Cell($this->value), Cell($another->value));

93. function swipe($lines)
{
return $lines->map(function ($line) {
$lineCopy = mergeLine($line);
while (!isLineMerged($lineCopy)) {
$lineCopy = mergeLine($lineCopy);
}
return $lineCopy;
});
}

94. EagerDesign
♞
Jumptotheproblemworthsolving
Eagerlyreplaceprimitiveswithtypes
Compose[thedomainalgebra] inside-out
Avoidmutablestate
#1
#2
#3
#4
@_md#EagerDesign

95. marcelloduarte
@_md
#EagerDesign

96. Thankyou!
♞
@_md
bit.ly/inviqa-contact bit.ly/inviqa-careers
#EagerDesign