Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Monads you've already put in production (withou...
Search
Tejas Dinkar
October 10, 2014
Technology
1
1.2k
Monads you've already put in production (without knowing it)
Tejas Dinkar
October 10, 2014
Tweet
Share
More Decks by Tejas Dinkar
See All by Tejas Dinkar
Quick Wins for Page Speed
gja
0
130
Progressive Web Apps In Clojure(Script)
gja
4
2.4k
Lightning - Monads you already use (without knowing it)
gja
1
390
Native Extensions Served 3 Ways
gja
0
350
Other Decks in Technology
See All in Technology
slog.Handlerのよくある実装ミス
sakiengineer
4
410
💡Ruby 川辺で灯すPicoRubyからの光
bash0c7
0
120
Generative AI Japan 第一回生成AI実践研究会「AI駆動開発の現在地──ブレイクスルーの鍵を握るのはデータ領域」
shisyu_gaku
0
310
会社紹介資料 / Sansan Company Profile
sansan33
PRO
6
380k
【NoMapsTECH 2025】AI Edge Computing Workshop
akit37
0
220
ハードウェアとソフトウェアをつなぐ全てを内製している企業の E2E テストの作り方 / How to create E2E tests for a company that builds everything connecting hardware and software in-house
bitkey
PRO
1
160
複数サービスを支えるマルチテナント型Batch MLプラットフォーム
lycorptech_jp
PRO
1
820
研究開発と製品開発、両利きのロボティクス
youtalk
1
530
新アイテムをどう使っていくか?みんなであーだこーだ言ってみよう / 20250911-rpi-jam-tokyo
akkiesoft
0
310
250905 大吉祥寺.pm 2025 前夜祭 「プログラミングに出会って20年、『今』が1番楽しい」
msykd
PRO
1
980
DDD集約とサービスコンテキスト境界との関係性
pandayumi
3
290
Aurora DSQLはサーバーレスアーキテクチャの常識を変えるのか
iwatatomoya
1
1.1k
Featured
See All Featured
The Web Performance Landscape in 2024 [PerfNow 2024]
tammyeverts
9
810
A designer walks into a library…
pauljervisheath
207
24k
Principles of Awesome APIs and How to Build Them.
keavy
126
17k
Writing Fast Ruby
sferik
628
62k
The Straight Up "How To Draw Better" Workshop
denniskardys
236
140k
Typedesign – Prime Four
hannesfritz
42
2.8k
Understanding Cognitive Biases in Performance Measurement
bluesmoon
29
1.9k
GitHub's CSS Performance
jonrohan
1032
460k
Building a Scalable Design System with Sketch
lauravandoore
462
33k
jQuery: Nuts, Bolts and Bling
dougneiner
64
7.9k
How to train your dragon (web standard)
notwaldorf
96
6.2k
Producing Creativity
orderedlist
PRO
347
40k
Transcript
Monads you are already using in prod Tejas Dinkar nilenso
about.me • Hi, I’m Tejas • Nilenso: Partner • twitter:
tdinkar • github: gja
Serious Pony
Online Abuse
Trouble at the Koolaid Point http://seriouspony.com/trouble-at-the-koolaid-point/ https://storify.com/adriarichards/telling-my-troll-story-because- kathy-sierra-left-t
If you think you understand Monads, you don't understand Monads.
None
This talk is inaccurate and will make a mathematician cry
None
Goal of this talk For you to say “Oh yeah,
I’ve used that hack”
None
Monads • Programmable Semicolons • Used to hide plumbing away
from you • You can say Monads in almost any sentence and people will think you are smart
None
Values Value
Monads Value Box
Mysore Masala Monad M onad Value
Monads Value Box
Monads • Monads define two functions • return takes a
value and puts it in a box • bind takes a box & function f, returning f(value) • it is expected that the function returns a box
Value Value Another Value Value Function return bind
Our Function Signatures Value f(value)
Some math (√4) + 5
Some math (√4) + 5 3 or 7!
Value 4
Monad [4]
[alive, dead]
ruby! x = [1, 2, 3] y = x.map {
|x| x + 1 } # y = [2, 3, 4]
return Value Value return
return def m_return(x) [x] end # m_return(4) => [4]
The functions Value f(value)
Square Root fn def sqrt(x) s = Math.sqrt(x) [s, -s]
end # sqrt(4) => [2, -2]
Increment Fn def inc_5(x) [x + 5] end # inc_5(1)
=> [6]
Bind Functions Another Value Value Function bind
Bind Function x = m_return(4) y = x.????? { |p|
sqrt(p) } # I want [-2, 2]
Bind Function x = m_return(4) y = x.map {|p| sqrt(p)
} # y => [[2, -2]] # ^—— Box in a box?
Bind Function x = m_return(4) y = x.mapcat {|p| sqrt(p)
} # y => [2, -2]
Putting it together m_return(4) .mapcat {|p| sqrt(p)} .mapcat {|p| inc_5(p)}
# => [3, 7]
You have invented the List Monad, used to model non-determinism
Congrats
Turtles all the way down
A small constraint • Let’s do a bit of a
self imposed constraint on this • Functions must return either 0 or 1 elements • (we’ll only model positive integers here)
return - stays the same
bind - stays the same x = m_return(4) y =
x.mapcat { |p| inc_5(p) } # y => 9
Square Root Fn def sqrt(x) if (x < 0) return
[] #error else [Math.sqrt(x)] end end # sqrt(4) => [2] # sqrt(-1) => []
Describe in English There is a list passed to each
step Maybe this list has just one element, or Maybe it has none
None
The Maybe Monad • The intent is to short circuit
computation • The value of the `box’ is None, or Just(Value) • You can think of it as a type-safe nil / null
try def try(x, f) if x == nil return f(x)
else return nil end end # 4.try { |x| x + 5 } => 9 # nil.try {|x| x + 5 } => nil
None
Let’s start over • The Monad Laws • Left Identity
• Right Identity • Associativity
Left Identity m_return(a).bind(f) == f(a)
Right Identity m.bind(m_return) == m
Associativity m.bind(f).bind(g) == m.bind(x -> f(x).bind(g))
Store Computation
The State Monad • Rest of the world - State
Machine (sorta) • The value inside the box f(state) => [r new-state] • Particularly useful in pure languages like Haskell • Let’s build a stack
The functions Value f(value)
The functions (f(value) state) [new-value, new-state]
push def push(val) lambda { |state| new_state = state.push(val) [value,
new_state] } end
pop def pop() lambda { |state| val = state.pop() [val,
state] } end
def double_top() lambda { |state| top = state.pop() [2 *
top, state.push(2*top)] } end double_top
return def m_return(x) lambda { |state| [x, state] } end
bind def bind(mv, f) lambda { |state| v, temp_state =
mv(state) state_fn = f(v) state_fn(temp_state) } end
example # Not working code ! m_return(4) .bind(a -> push(a))
.bind(b -> push(b + 1)) .bind(c -> double_top()) .bind(d -> sum_top2()) .bind(e -> pop())
None
Associativity m.bind(f).bind(g) == m.bind(x => f(x).bind(g))
turn this # Not working code ! m_return(4) .bind(a ->
push(a)) .bind(b -> push(b + 1)) .bind(c -> double_top()) .bind(d -> sum_top2()) .bind(e -> pop())
into this m_return(4) .bind(a -> push(a) .bind(b -> push(b +
1) .bind(c -> double_top() .bind(d -> sum_top() .bind(e -> pop())))))
done with ruby
imagine # Not working code state_monad { a <- m_return(4)
b <- push(a) c <- push(b + 1) d <- double_top() e <- sum_top2() pop() }
Back to List m_return(4) .mapcat {|p| sqrt(p)} .mapcat {|p| inc_5(p)}
# => [3, 7]
Back to List m_return(4) .mapcat {|a| sqrt(a) .mapcat {|b| inc_5(b)}}
# => [3, 7]
Back to List list_monad { a <- m_return(4) b <-
sqrt(a) c <- inc_5(b) c }
On to Clojure • this is an example from clojure.net
• the state is a vector containing every function we’ve called so far
(defn inc-s [x] (fn [state] [(inc x) (conj state :inc)]))
in clojure (defn inc-s [x] (fn [state] [(inc x) (conj
state :inc)])) (defn do-things [x] (domonad state-m [a (inc-s x) b (double-s a) c (dec-s b) d (dec-s c)] d)) ! ((do-things 7) []) => [14 [:inc :double :dec :dec]]
state monad in Clojure (defmonad state-m "Monad describing stateful computations.
The monadic values have the structure (fn [old-state] [result new-state])." [m-result (fn m-result-state [v] (fn [s] [v s])) m-bind (fn m-bind-state [mv f] (fn [s] (let [[v ss] (mv s)] ((f v) ss)))) ])
state monad in Haskell inc = state (\st -> let
st' = st +1 in (st’,st')) inc3 = do x <- inc y <- inc z <- inc return z
Finally, IO
IOMonad • rand-int(100) is non deterministic !
ay-yo
IOMonad • rand-int(100) is non deterministic • rand-int(100, seed =
42) is deterministic • monadic value: f(world) => [value, world-after-io]
IOMonad • puts() just `appends to a buffer’ in the
real world • How does gets() return different strings? • gets() returns a fixed value based on the `world’
Image Credits http://www.myfoodarama.com/2010/11/masala- dosa.html http://www.clojure.net/2012/02/10/State/ http://www.cafepress.com/ +no_place_like_home_ruby_slippers_3x5_area_rug, 796646161 http://www.netizens-stalbans.co.uk/installs-and- upgrades.html.htm
http://www.hpcorporategroup.com/what-is-the-life- box.html
Thank You MANY QUESTIONS? VERY MONAD SO FUNCTIONAL Y NO
CLOJURE?
[email protected]
@tdinkar WOW WOW WOW MUCH EASY SUPER SIMPLE