1. Time Travel!
Predicting the Future !
and Surviving a Parallel Universe !
Hossam Karim!

2. The Free Lunch is Over!!

3. Welcome to the Real World!

4. Concurrency!

5. It’s Pretty Hard!

6. Concurrency Pain!

7. Doubled-Checked Locking Problem
!"#$%&!&$'((!"#$%&'()'*+',-#*+./0!1!
!!
!!!!)%*'+,!234'/5.6'7'5#$8*'!'34'/5.6'7'5#$8*'9!
!!
!!!!"#$%&!234'/5.6'7'5#$8*'!0':234'/5.6'7'5#$*';<!1!
!!!!!%-!;'34'/5.6'7'5#$8*'!==!."$$<!
!!!!!!!'34'/5.6'7'5#$8*'!=!.,/!234'/5.6'7'5#$8*';<9!
!!!!!),+").!'34'/5.6'7'5#$8*'9!
!!!>!
!!
!>!

8. Doubled-Checked Locking Problem
!"#$%&!&$'((!"#$%&'()'*+',-#*+./0!1!
!!
!!!!)%*'+,!234'/5.6'7'5#$8*'!'34'/5.6'7'5#$8*'9!
!!
!!!!"#$%&!234'/5.6'7'5#$8*'!0':234'/5.6'7'5#$*';<!1!
!!!!!%-!;'34'/5.6'7'5#$8*'!==!."$$<!1!
!!!!!!!(/.&0)1.%2,3!;"#$%&'()'*+',-#*+./0>&$'((<!1
!!!!!!!!!'34'/5.6'7'5#$8*'!=!.,4!234'/5.6'7'5#$8*';<9!
!!!!!!!?!
!!!!!?!
!!!!!),+").!'34'/5.6'7'5#$8*'9!
!!!?!
!!
!?!

9. Doubled-Checked Locking Problem
!"#$%&!&$'((!"#$%&'()'*+',-#*+./0!1!
!!
!!!!)%*'+,!234'/5.6'7'5#$8*'!'34'/5.6'7'5#$8*'9!
!!
!!!!"#$%&!234'/5.6'7'5#$8*'!0':234'/5.6'7'5#$*';<!1!
!!!!!%-!;'34'/5.6'7'5#$8*'!==!."$$<!1!
!!!!!!!(/.&0)1.%2,3!;"#$%&'()'*+',-#*+./0>&$'((<!1!
!!!!!!!!!%-!;'34'/5.6'7'5#$8*'!==!."$$<!
!!!!!!!!!!!'34'/5.6'7'5#$8*'!=!!
!!!!!!!!!!!!!!!.,4!234'/5.6'7'5#$8*';<9!
!!!!!!!?!
!!!!!?!
!!!!!),+").!'34'/5.6'7'5#$8*'9!
!!!?!
!!
!?!
!!
!

10. Doubled-Checked Locking Problem
volatile
Thread A
Thread B
Processor Main
Cache Memory
synchronized

11. Doubled-Checked Locking Problem
!"#$%&!&$'((!"#$%&'()'*+',-#*+./0!1!
!!
!)%*'+,!*-$'+%$,!234'/5.6'7'5#$8*'!'34'/5.6'7'5#$8*'9!
!!
!!!!"#$%&!234'/5.6'7'5#$8*'!0':234'/5.6'7'5#$*';<!1!
!!!!!%.!;'34'/5.6'7'5#$8*'!==!/"$$<!1!
!!!!!!!(0/&1)-/%2,3!;"#$%&'()'*+',-#*+./0>&$'((<!1!
!!!!!!!!!%.!;'34'/5.6'7'5#$8*'!==!/"$$<!
!!!!!!!!!!!'34'/5.6'7'5#$8*'!=!!
!!!!!!!!!!!!!/,4!234'/5.6'7'5#$8*';<9!
!!!!!!!?!
!!!!!?!
!!!!!),+")/!'34'/5.6'7'5#$8*'9!
!!!?!
!!
!?!

12. Scala
!"#$$!"#$%$&'(()*+,%(-.(#/(01*#/234!5!
!!!!
!!!"#%&!'#"!(67(3829(:(8*+'#(!;!()*!<67(3829(:(8*+'#(!
!!
=!
!
Decompiled into Java
!!"#$$!"#$%$&'(()*+,%(-.(#/(01*#/234!%&'"(&()*$!!"#$#%&'(")!5!
!!!'+%,#*(!678(392:(;(9*+'#(!(78(392:(;(9*+'#(<!
!!!'-."%!!,/"#*%"(!%)*!,2=>$8?@<!
!!
!!!'-."%!!678(392:(;(9*+'#(!(78(392:(;(9*+'#(AB!5!
!!!!!%0!AA*1%$C,2=>$8?@!D!@7EB!FF!@B!
!!!!!$2)!1+/)%3(4!A*1%$B!5!
!!!!!!!%0!AA*1%$C,2=>$8?@!D!@7EB!FF!@B!5!
!!!!!!!!!*1%$C(78(392:(;(9*+'#(!F!)(5!678(392:(;(9*+'#(AB<!
!!!!!!!!!*1%$C,2=>$8?@!GF!E<!
!!!!!!!H!
!!!!!!!+(*-+)!*1%$C(78(392:(;(9*+'#(<!
!!!!!H!
!!!H!
!H!
!!
!

13. Concurrency Models!

14. Concurrency Models
!"#$%&&'#()*&"+&,--.#+)
/"0'1
!"--%#.$,(."# 23#$4&"#.5,(."#
24,&'0)/'-"&3 /'66,+')*,66.#+ 7%6389,.(.#+ 71"$:.#+
2'-,;4"&'6 /"#.("&6

15. Multi-threading Approach!

16. Thread Pools and Executors
!
!!!"#!"#$%&'()%*&+,,-./#0%12!34/5!4'()%*&12!34/6!7!
!!!!!$%&!8,,-!9!:$%;</,)1=4%>?#$%&'()%*&+,,-.4'()%*&16!
!!!!!$%&!)%1<-/!9!@%4;(0*)A./#0%')*B%-C%"#4#/#,46!7!
!!!!!!!#48</!!!
!!!!!!!!!#'(!.D!E!F!/,!/#0%16!7!
!!!!!!!!!!!8,,-=%$%;</%!7!
!!
!!!!!!!!!!!!!)"*!!"##$%&'!7!
!!!!!!!!!!!!!!!!"#!)<4.6!7!
!!!!!!!!!!!!!!!!!%4;&%;.#48</6!
!!!!!!!!!!!!!!!G!
!!!!!!!!!!!!!G!
!!
!!!!!!!!!!!G!
!!!!!!!!!G!
!!!!!!!!!8,,-=1(</&,>4.6!
!!!!!!!!!8,,-=*>*#/'%)0#4*/#,4.F5!()*'+#),=H3IJ':K6!
!!!!!G!
!!!!!-,L=#4",.M"#$%&'()%*&+,,-2!C,4%!N&!O,@1!<1#4L!N&!'()%*&1!#4!N&!01M=!
!!!!!!!",)0*/./#0%15!4'()%*&15!)%1<-/=/#0%H#--#166!
!!G!
!!

17. Java Fork-Join Framework!

18. Fork-Join Framework
join
fork
join
ForkJoinTask fork
fork
join
Deque Worker
per Worker Thread Thread Pool
!"#$% !&!%'()*+,%
fork
-./0
'*)*+,% Work
Stealing
!&!%'()*+,%
!"#$%
fork

19. Fork-Join Framework
!
!!"#$$!"#$%&'()#*%+,-'./!
!!#0#+#12'3!4&&-5671289!'2-&23!7129!#1:3!7129!2;&#';<0:3!712=!!
!!!%&'%()$!!"#$%&'()#,-'.6><1?8!@!
!!
!!!!!-''#&2/!
!!!!!!2;&#';<0:!AB!CDD!EE!2;&#';<0:!FB!CDDD9!!
!!!!!!G,;&#';<0:!+%'2!H#0<1?!2<!6CDD9!CDDD8G=!
!!
!!!!!)%*!$<+I%2#3!><1?!B!@!
!!!!!!!+*!//#1:!J!'2-&2=!F!2;&#';<0:=!
!!!!!!!!!#0#+#12'K'0($#/'2-&29!#1:=K'%+!
!!!!!!!%"$%!@!
!!!!!!!!!,#"!+(::0#!B!/#1:!L!'2-&2=!AAA!C!
!!!!!!!!!,#"!0#M2!B!!(%-!"#$%&'()#*%+,-'./#0#+#12'9!'2-&29!+(::0#9!2;&#';<0:=!
!!!!!!!!!,#"!&(?;2!B!(%-!"#$%&'()#*%+,-'./#0#+#12'9!+(::0#9!#1:9!2;&#';<0:=!
!!
!!!!!!!!!0#M2KM<&.!
!!!!!!!!!&(?;2KM<&.!
!!
!!!!!!!!!0#M2KN<(1!L!&(?;2KN<(1!
!!!!!!!O!
!!!!!O!
!O!

20. Fork-Join Framework
!
!!"#!"#$%&#'()*+,-.-+-(/01!2(/3!/4$-04#.51!2(/3!67$7..-.'0+1!2(/8!9!
!
!!!!!$%&!6##.!:!'"(!;#$%&#'(<##.,67$7..-.'0+8!
!
!!!!!$%&!0*+=70%!:!!
!!!!!!!'"(!>-?*$0'@-)*+=70%,,A!/#!-.-+-(/08B/#C$$7D3!E3!-.-+-(/03!/4$-04#.58!
!
!!!!!$%&!$-0*./!:!F-(?4+7$%,0*+=70%8!9!
!!!!!!!'(6*/!!!6##.B'(@#%-,'(6*/8!
!!!!!G!
!
!!!!!6##.B04*/5#H(,8!
!
!!!!!.#IB'("#,!
!!!!!!!!J"#$%&#'()*+1!0*+!:!K53!5#(-!'(!K5!+0JB!
!!!!!!!!!!!"#$+7/,$-0*./B@7.*-3!$-0*./B/'+-L'..'088!
!!!
!G!
!!
!

21. Parallel Collections!

22. Parallel Collections - Mathematica
ParametricPlot3D CosΦ SinΘ, SinΦ SinΘ, CosΘ,
In[1]:= plotSpherefactor_ :
Φ, 0, 2 Π, Θ, 0, Π, PlotPoints 100, Mesh None,
ColorFunction Functionx, y, z, Φ, Θ,
HueSinfactor Φ Sinfactor Θ, ColorFunctionScaling False,
Axes None, Boxed False, ImageSize 100
LaunchKernels
DistributeDefinitionsplotSphere
Out[2]= KernelObject1, local, KernelObject2, local,
KernelObject3, local, KernelObject4, local,
KernelObject5, local, KernelObject6, local,
KernelObject7, local, KernelObject8, local
Out[3]= plotSphere

23. Parallel Collections - Mathematica

24. Parallel Collections - Mathematica

25. Scala Parallel Collections
!!!#!#$%#'$()#*+!#',!-#%'*+!$%'().+!*+%,/#'0!1!2!
!!!!!-./!(34%56'),!78%94%56').!1!
!!!!!!!:'5%8*()#*;#$%+!=.;!
!!!!!!!!!34(!
!!!!!!!!!!!-#'!!!(0!#'(?@$A@$?;-8*34%()#*;B'%C4%6,!-#'...;!
!!!!!!!!!4*%#%#87(;B'%D43';'7)$E#%6(-#%'*..!
!!
!!!!!-./!56#)F#*'5%8*#'$!1!78%94%56');4BB*'B4%'(:'5%8*;'3%G/#'0.(!
!!!!!2!
!!!!!!!(H'5%8*,!-#'.!!!
!!!!!!!!!'#!(-#';#$F#*'5%8*G.!H'5%8*!+I!-#'!/1!H'5%8*!
!!!!!J!
!!!!!,!!II!.!
!!
!!!!!34%56')!II!56#)F#*'5%8*#'$;-8)K'-%(:'5%8*;'3%G/#'0.!2!
!!!!!!!(H'5%8*,!)#*.!!!H'5%8*!II!#$%#'$()#*,!-#%'*.!
!!!!!J!
!!!J!

26. Scala Parallel Collections
!!!#$%'()!
!!!!#!%*#+%(*,()-!
!!!!!$)).!$%'(/+%(01!2%'*.!$%'(/+%(01!3%#('.!)(*+,4.!$%'(/+%(0!5!6!
!!
!!!!!!#!*7%#-2%'.!+%(4.!-$%'(/+%(01!$%'(/+%(04!5!6!
!!!!!!!-./!-8$#)9(21!:;#$#)9(24!5!
!!!!!!!!!=()#;'-2%'%*#.!?@4!
!!!!!!!!!!!8$7-!
!!!!!!!!!!!!!3%(!!!+0!+%(-AB*CB*A3;'8$#-2%'D(#E$#91!3%(444!
!!!!!!!!!!!7$'#%#%;:-?D(#F$8((:2*G%#9-3%#('44!
!!
!!!!!!!-8$#)9(21!:;#$#)9(24!
!!!!!H!
!!
!!!!!*#!-2%'*%*I87#J4!
!!!!!!!$))!
!!!!!/1!6!
!!!!!!!-./!-8$#)9(21!:;#$#)9(24!5!
!!!!!!!!!2%'*8$7-*7%#4'(2K)(L(3#--M1!J4!!!-M?N!OO!J?N1!M?P!OO!J?P44!
!!
!!!!!!!-./!)9%2Q%'()#;'%(*!5!:;#$#)9(2$DD'(D$#(-=()#;'(87#J/+%(04-!
!!!!!!!6!
!!!!!!!!!-R()#;'1!3%(4!!!
!!!!!!!!!!!*#!-3%(%*Q%'()#;'J4!R()#;'!.O!3%(!/1!R()#;'!
!!!!!!!H!
!!!!!!!1!?!OO!?4!
!!
!!!!!!!%*#+%(*,()-$))!OO!8$#)9(21!)9%2Q%'()#;'%(*1!3%#('4!
!!!!!H!
!!!H!

27. Scala Parallel Collections
!
!!!#!#$%#'$()*)'+,#*-!#'.!/#%'*-!$%'()0-!()*1'2%3*4#'5!6!7!
!!!!!*+,!+8)%29',.!:3%;)%29',0!6!
!!!!!!!1'2%3*+,#*#$%-!=0-+!
!!!!!!!!!8)?+!
!!!!!!!!!!!/#'!!!(.!#'+@A$BA$@/3*8)%+,#*C'%()%9.!/#'000!
!!!!!!!!!?)*%#%#3:+=C'%D)8'':,$E#%9+/#%'*00!
!!
!!!!!*+,!29#,F#*'2%3*#'$!6!:3%;)%29',-+)CC*'C)%'+1'2%3*'8?%G4#'50+!
!!!!!7!
!!!!!!!+H'2%3*.!/#'0!!!
!!!!!!!!!'#!+/#'#$F#*'2%3*G0!H'2%3*!-I!/#'!,/!H'2%3*!
!!!!!J!
!!!!!.!=!II!=0!
!!!!!8)%29',!II!29#,F#*'2%3*#'$-+/)%;)?+#$%#'$()*)'+=.!/#%'*00!
!!!J!
!!
!

28. Scala Parallel Collections

29. Message Passing!

30. Akka Actors
!#$%'(#)*
!#$% !#$% !#$%
2%$3/)456$%7
'()%*+,$%,
8%)970$:1
,9/9#+$1
;),($1,)
-.+/0%)1
!#$% !#$% !#$% !#$% !#$% !#$%
!
3).9*+$%@ !#$%
%))+*)
!#$%
=9+/3$?
=),,9) %)(/A@4),,9)

31. Akka Actors
!
!#$%!#$$!#$%'('))#*'+$'))#*',!'()*+,-!
!!
!
!
!-%.!).$%'/01234)1'$+-!5!
!!!!!/#!)4)1'$!6!/01234)1'$+7$#.8/01234)1'$7-!
!
!!!!!/#!)#$%'/0123!6!!
!!!!!!!)4)1'$9#0123:;+32%)=#$%'/0123?!8#$'!6!7)#$%'/01237-!
!
!!!!!/#!@''*#1'/0123!6!!
!!!!!!!)4)1'$9#0123:;+32%)=A''*#1'/0123?!8#$'!6!7@''*#1'/01237-!
!
!!!!!)#$%'/0123!B!7C'27!
!!!!!)#$%'/0123!B!#$%'('))#*'+7DAEFGHIG7-!
!
!!!!!)4)1'$9)CJ1@2K8+-!
!L!
!!
!
!

32. Akka Actors
!
!!#$$!#$%'()*+,!%'%()$!!#$%!-!
!!
!!!*#!+.!/!0+..12.3)+2*'4*5676*'$8!'+,$9!
!!
!!!*#!:''.#*'()*+,!/!!
!!!!!!)+2*'4*5#)*+,;+,3#==#??$#12()*+,76*'$?@6',?:''.#*'()*+,9!
!
!!!)%-!,')'1A'!/!-!
!!!!!!#$%!6!.'/,(0!!!
!!!!!!!+.512B+369!
!
!!!!!!#$%!+*C',!!!!!!!
!!!!!!!+.512B+3D#2E*!C#2:'!*C16!+2'8!F1!:''.#*'!*+!#2+*C',!#)*+,9!
!!!!!!!:''.#*'()*+,!G!+*C',!
!!!H!
!H!
!!
!

33. Akka Actors
!
!!#$$!#$#%'#()'*+!%'%()$!!#$%!,!
!!!*#!$*%!-!.*%%/0%1)*0'#2'3454'#67!'+,$8!
!!
!!!)%-!+#)#/9#!-!,!
!!
!!!!!!#$%!:6;$##44%#16#44%#8!!!
!!!!!!!$*%3/0=*1?#)#/9#@!6#44%#!A43=*+6'16#44%#88!
!!
!!!B!
!B!
!!
!

34. Akka Futures
./0$1-$2!#$%3)*4,$5
!#$%+,*$-
!#$%3)*4,$./0$1--)6(%
!#$%'#(()(*
76(%4#-(189$:4$%-
9$16;;$(2-)6(% 3)((1)#
76(%4#-(-%

35. Akka Futures
!
!!#!#$#%'$%($)*+,!!#$%-'(#-'$%($).'/0$*1233!4!
!!!$%!5!
%#$%+,*$-./-0, !!!!!'(/+6*)#%78(/#9!:!!
!!!!!!!7+(/+;(%)$0$1%!=!'(/+6*)#%?#+$7'()!@($99AB(C;1-'(/+6*)#%3!
!!!!!!!!!+$%($)*+!:!!
!!!!!!!!!!!6#$#%A$%(8%+7012+#/$(20.0$1%+97!
!!!!!!!!!!!!!(0$1%!!!7(0$1%!=!'$%($).?#+$78(/#99AB(C;1-'$%($).'/0$*1239!
!#$%1)*2,$3$42$%-
!!!D!*+(#,!+$%($)*+!
!!
!#$%1)*2,$ -!#!#$#%01BB2E($*12+,!!#$%-'(#-)#$*#%+,33!4!
!!!#$#%'$%($)*+AB(C7!
!!!!!/*+$F'$%($).'/0$*12!!
/*+$F'$%($).'/0$*12A/($G(C7HA%01BB2E($*12+99!
!!
!#$%'#(()(* !-,-$*53$42$%- !
3$/066$(7-)0(% /0(%2#-(/5./-0,
/0(%2#-(/5./-0,
/0(%2#-(/5./-0,

36. Akka Futures
!
!!#!#$#%'$%($)*+,!!#$%-'(#-'$%($).'/0$*1233!4!
!!!$%!5!
!
!!!!!'(/+6*)#%78(/#9!:!!
!!!!!!!7+(/+;(%)$0$1%!=!'(/+6*)#%?#+$7'()!@($99AB(C;1-'(/+6*)#%3!
!
!!!!!+$%($)*+!:!!
!!!!!!!6#$#%A$%(8%+7012+#/$(20.0$1%+97!
!!!!!!!!!!!!!(0$1%!!!7(0$1%!=!'$%($).?#+$78(/#99AB(C;1-'$%($).'/0$*1239!
!
!!!D!*+(#,!+$%($)*+!
!!
-!#!#$#%01BB2E($*12+,!!#$%-'(#-)#$*#%+,33!4!
!!!#$#%'$%($)*+AB(C7!
!!!!!/*+$F'$%($).'/0$*12!!
/*+$F'$%($).'/0$*12A/($G(C7HA%01BB2E($*12+99!
!!

37. !
Akka Promises
!!!!#$!!%##!#$#%'($)%*+!'()*+,!
!!
!!!!%##!-.(*/01*0#!2!!
!!!!!,%!3#*1!4!56#./3#*1'7$88$7,!
!!!!!)-.%)!)'!,%!*6!4!3#*19:;$#6=*/!!
!!
!!!!!/$0!)*$**))?@%/A%#%/*+!!#$%'B#$#%C!4!2!
!!!!!!!,%!D.(*/01*0#E/.1;*!4!E/.1;*B#$#%C',!
!!!!!!!A%#%/*!2!:..1*FG#/*1*)3H$/:#%II'D.(*/01*0#E/.1;*,!J!
!!!!!!!).D9;0I.'7K*L/*!#=*!D.(*/01*0#M!:.0L#!6$))!%M!N*!N;))!6$))!3.%7,!
!!!!!!!D.(*/01*0#E/.1;*!
!!!!!J!
!!
!!!!!/$0!:..1*FG#/*1*)3H$/:#%II'/.1;*+!!#$%'B#$#%C,!2!
!!!!!!!).D9;0I.'!
!!!!!!!!!7K*L/*!#=*!D.(*/1*0#M!N*!);(*!;0!$!$/$))*)!N./):!6$))*:+!O79!
!!!!!!!!!!!I./1$#'=/*$:96%//*0#=/*$:',9D*#P$1*,,!
!!!!!!!).D9;0I.'!
!!!!!!!!!7K*L/*!#=*!D.(*/01*0#M!N*L/*!D.;0D!#.!)**!I./!$!N=;)*7,!
!!!!!!!=/*$:9)**'QRRR,!
!!!!!!!/.1;*9%66*'#$#%'7K.0:*/I%)7,,!
!!!!!J!
!!
!!!!!/$0!#=$08503N$3',!2!
!!!!!!!3#*19=%#:.N0',!
!!!!!J!
!!!J!
!!
!

38. Akka Promises
!
!!!!#!#$%'()*+,-!.!
!!
!!!!!$%!/)0$#*1$*(!2!'(!3)0$#*1$*(!
!!
!!!!!$%!/)0$#*1$*(4#)1+$!2!/)0$#*1$*(56$7+$8$669+:;#;(;#$!
!!
!!!!!6)/5*=),?$@#$!(A$!$)6$B!C$!7+D$%!E);!7!F;$+()*-!
!!
!!!!!!!#$%'()*+$*,-./%0+1-+12($2+$$-34)%*)%/05$$6)--3-3!
!!!!!GC7(5#$7%E,/)0$#*1$*(4#)1+$B!HI!+$')*%+-!!!%/786-5/1!
!!
!!!!!/)0$#*1$*(4#)1+$!)*J;''$++!.!
!!!!!!!)%*!J(7(;+,076;$-!!!
!!!!!!!!!6)/5*=),!
!!!!!!!!!!:;#!/)0$#*1$*(!=*766E!#$6$%B!(A$E!+7E!(@+!K+5=)#17(,076;$--!
!!!!!L!)*76;#$!.!
!!!!!!!)%*!$!!!
!!!!!!!!!6)/5$##)#,:)+B!+)##E5!3))%!6;'D!*$M(!(1$!N--!
!!!!!L!
!!
!!!!!/)0$#*1$*(5(A7*D+G*EC7E,-!
!!!L!
!!
!!
!

39. Relations to Functional Programming!
Selected
Topics

40. Monoid
!#$%'()
!*%%$+,-.,/,.0)
!12(3.,.0)
!#$#%'(('!)#*#+ !#$#%#)#*#+
,!#$'(('!%#)-'(('!*#+ !#$#%#)#*#+
!#$'((',!%#)'(('!*#+-
!#$#%'(('! !#$#%
!'(('!#$#%

41. Monoid
!#$%
'()*%+
,-.+.//%/0
1%+2%

42. Immutable Data Structures – Google’s Guava
!
!!#$%!!#$#$%'()!**+$,-./01../2$1'345!6!
!!!!!!#$#$%'()!3$%'(3!7!
!!!!!!!%'$()*+!#$8#$%'())'*,+-458!
!!!!!!!!!,994:;11(./3:58!
!!!!!!!!!,994:;+,=,:58!
!!!!!!!!!,994:+.9/%3:58!
!!!!!!!!!-+.945?!
!!!!!..#$-/0#1(,,2345$675##)*+389!
!!!!!'()'*!3$%'(3?!
!!!@!
!!
h.p://code.google.com/p/memory-­‐measurer/wiki/ElementCostInDataStructures
!
Immutable Data Structures – Scala
!
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43. Persistent Data Structures
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44. Thank You!