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
Continuation is to be continued
Search
Masayuki Mizuno
April 22, 2025
1
1.4k
Continuation is to be continued
Masayuki Mizuno
April 22, 2025
Tweet
Share
More Decks by Masayuki Mizuno
See All by Masayuki Mizuno
Omotesando.rb #110
fetburner
0
140
callccの実装を読む
fetburner
0
170
RubyでSlackのbotを作ろう
fetburner
0
160
継続オペレータの話
fetburner
0
230
Rubyでリストモナドを使う
fetburner
0
180
次世代のプロファイラVernierを試す
fetburner
0
120
数値計算とメモリ最適化
fetburner
0
240
3/14なので円周率を計算する
fetburner
0
400
ネットワーク機器の中の OCaml
fetburner
1
730
Featured
See All Featured
The World Runs on Bad Software
bkeepers
PRO
71
11k
Why Our Code Smells
bkeepers
PRO
339
57k
Bash Introduction
62gerente
615
210k
Faster Mobile Websites
deanohume
310
31k
YesSQL, Process and Tooling at Scale
rocio
173
14k
Producing Creativity
orderedlist
PRO
347
40k
The Straight Up "How To Draw Better" Workshop
denniskardys
237
140k
Speed Design
sergeychernyshev
32
1.1k
Git: the NoSQL Database
bkeepers
PRO
431
66k
Music & Morning Musume
bryan
46
6.8k
Building an army of robots
kneath
306
46k
The Illustrated Children's Guide to Kubernetes
chrisshort
48
51k
Transcript
©2025 Wantedly, Inc. Continuation is to be continued A revisit
of first-class continuations or an invitation to delimited continuations RubyKaigi 2025 Mar 16, 2025 - Masayuki Mizuno
©2025 Wantedly, Inc. .BTBZVLJ.J[VOP "CPVUNF • Backend engineer at Wantedly,
Inc. • Born in Takamatsu City, Kagawa • Programming language lover
©2025 Wantedly, Inc. 1. What is a continuation? 2. Continuations’
use cases: backtracking 3. call/cc’s problem 4. Better alternative: shift/reset 5. Conclusion Agenda
©2025 Wantedly, Inc. 8IBUJTDPOUJOVBUJPO
©2025 Wantedly, Inc. What is a continuation? Computation that receive
the evaluation result Or run-time point in program execution
©2025 Wantedly, Inc. Ruby’s built-in continuation operator: call/cc Call/cc captures
current continuation Kernel.#callcc / Continuation#call behaves like setjmp / longjmp
©2025 Wantedly, Inc. Calling continuation multiple times Continuation can be
invoked arbitrary times However, terminated fiber cannot be called Let's see how call/cc is special, using a DSL as an example
©2025 Wantedly, Inc. $POUJOVBUJPOT`VTFDBTFT CBDLUSBDLJOH
©2025 Wantedly, Inc. $BOXFXSJUFCBDLUSBDLJOHGMVFOUMZ :PVDBOEPJUJO)BTLFMM $POUJOVBUJPOT`VTFDBTFTCBDLUSBDLJOH
©2025 Wantedly, Inc. /BJWFUSBOTMBUJPOMFBETUPDBMMCBDLIFMM 8BOUBNPSFSFTFNCMBODFUP)BTLFMMTPOF $POUJOVBUJPOT`VTFDBTFTCBDLUSBDLJOH
©2025 Wantedly, Inc. .FUBQSPHSBNNJOHBWPJETDBMMCBDLIFMM #VJME"45GPSSFTPMWJOHWBSJBCMFTDPQF *OUSPEVDUJPOPGlEPzTZOUBYMJLF%4-
©2025 Wantedly, Inc. &WFSZTZOUBYOFFETSFJOWFOUJPO 5IF%4-JOUFSQSFUFSIBTUPSFQSPEVDFQSFUUZNVDIFWFSZUIJOH *TTVFPGNFUBQSPHSBNNJOHCBTFEBQQSPBDI
©2025 Wantedly, Inc. *ODPNQBUJCMFWBSJBCMFTDPQF .BOVBMWBSJBCMFQBTTJOHJTSFRVJSFE *TTVFPGNFUBQSPHSBNNJOHCBTFEBQQSPBDI
©2025 Wantedly, Inc. Implementing DSL with call/cc Ruby-level backtracking by
call/cc Thanks to one-pass evaluation, most Ruby expressions are also viable in DSL
©2025 Wantedly, Inc. 1SPCMFNPGDBMMDD
©2025 Wantedly, Inc. Problem of call/cc (1/2) Captures unnecessarily large
code pieces Need call/cc calls in two different places, one for backtracking and one for conclusion
©2025 Wantedly, Inc. 1PPSQFSGPSNBODF DBMMDDCBTFEDPEFCMPBUTVQJONFNPSZBOE$16DPOTVNQUJPO 1SPCMFNPGDBMMDD Let's discover the
cause for performance degradation
©2025 Wantedly, Inc. 5JHIUMZDPVQMFEXJUI7.JOUFSOBMT *NQMFNFOUBUJPOMJFTXJUIJO$3VCZ *OTJEFlDPOUJOVBUJPOzMJCSBSZ
©2025 Wantedly, Inc. 3FDPSETOBQTIPUPG7.TUBUF 4BWF7.TUBDLBOENBSLSVOUJNFQPJOU *NQMFNFOUBUJPOPG,FSOFMDBMMDD
©2025 Wantedly, Inc. %JGGFSFOUJBMTOBQTIPUPG7.TUBDL 3FVTFQSFWJPVT7.TUBDLCBDLVQJGUIFSFJTPOF ,FSOFMDBMMDD`TPQUJNJ[BUJPO
©2025 Wantedly, Inc. 3FTUPSFTTUBDLBOEQFSGPSNlMPOHKNQz *OTJEFPG$POUJOVBUJPODBMM 0WFSBMM DBMMDDEFWPUFTFYFDVUJPOUJNFTUPCBDLVQBOESFTUPSFPGTUBDL
©2025 Wantedly, Inc. #FUUFSBMUFSOBUJWFTIJGUSFTFU
©2025 Wantedly, Inc. shift/reset: yet another continuation operators Captures delimited
code block from shift to reset Unlike call/cc, delimited continuation will go back when reaches reset
©2025 Wantedly, Inc. Implementing “do” syntax like DSL with shift/reset
Delimiting continuation leads to simple code Enumerable#flat_map can be used as is
©2025 Wantedly, Inc. Implementing shift/reset with call/cc shift/reset are reproducible
by call/cc Thread-local variable is needed to record return addresses
©2025 Wantedly, Inc. Benchmarking “do” syntax like DSL with shift/reset
Delimited continuation improves performance Kernel.#callcc’s optimization may be effective for shift/reset implementation
©2025 Wantedly, Inc. Foresight to native shift/reset implementation shift/reset may
provide optimization hints Programmers can specify necessary stack range to the interpreter
©2025 Wantedly, Inc. $PODMVTJPO
©2025 Wantedly, Inc. 1. call/cc can manipulate continuations 2. call/cc
is sometimes suitable for DSL 3. call/cc has some problems • Hard to use for developers • Poor performance 4. shift/reset probably resolve problems of call/cc • I'm going to introduce the new, performant API Conclusion