Making Swift Even More Functional

- Swift Summit

Hello, I’m Veronica Ray!

Swift is great, but it could be better

Time to make change is now

–The Recurse Center User’s Manual

“Be rigorous. Understand how and why your code works. Understand your

tools. If you're working with a framework (like Sinatra or Flask), learning to use it is just scratching the surface. Go deeper. Learn how it

works.”

– Functional Programming In Swift

“Functional programmers emphasize that each

program can be repeatedly broken into smaller and

smaller pieces; all these pieces can be assembled using function application

to define a complete program.”

– Functional Programming In Swift

“Functional programming…emphasizes the importance of programming with values,

free of mutable state or other side effects.”

CLASS VS

STRUCT

WHY FUNCTIONAL?

•Helps you write clear and concise code

•Makes concurrency easier

•Reduces complexity

vs

SIMPLICITY

COMPARED TO SCALA

Too many custom operators and not opinionated enough

FP IN SWIFT•list comprehensions

•tail call optimization

FP IN SWIFT•list comprehensions

•tail call optimization

LIST COMPREHENSIONS

POWERFUL

PYTHON

PYTHON

BYTE CODE

PYTHON FOR LOOP

BYTE CODE IS 23 LINES!

vs

BYTE CODE IS THE SAME

SPELLING CORRECTOR

CONCISENESSReading code

Writing code

ADDING IT TO SWIFT

FP IN SWIFT•list comprehensions

•tail call optimization

RECURSION

TAIL CALL

TAIL RECURSIVE CALL

STACK TRACE(fact 3) (fact-tail 3 1) (fact-tail 2 3) (fact-tail 1 6) (fact-tail 0 6) 6

NOT TAIL RECURSIVE

STACK TRACE(fact 3) (* 3 (fact 2)) (* 3 (* 2 (fact 1))) (* 3 (* 2 (* 1 (fact 0)))) (* 3 (* 2 (* 1 1))) (* 3 (* 2 1))

TAIL CALL OPTIMIZATION

NOT GUANRANTEED

SWIFT CODE

BYTE CODE

jne to the label containing the conditional jump

BLOW OUT THE STACK

HOPE?

CHANGE YOUR BYTECODE

CHANGE YOUR LIFE

RECURSION KILLS

RADAR

LEARN MORE

•Functional Swift Conference •Open Radar •Dev Forums •Twitter •Natasha The Robot’s Blog

WHEN SWIFT GOES OPEN SOURCE

TIME TO MAKE CHANGE IS NOW