View
4.073
Download
0
Category
Tags:
Preview:
DESCRIPTION
Citation preview
Groovy, Kotlin, Scala or Java?
Andrey Breslav
Who's More Functional
1Wednesday, October 3, 12
About Me
• Project lead of Kotlin ➡ at JetBrains since 2010
• EG member of JSR-335➡ Project Lambda
2
Andrey Breslav
2Wednesday, October 3, 12
Prologue
3
3Wednesday, October 3, 12
Prologue– Dad (or Mom), is Java a
functional language?
3
3Wednesday, October 3, 12
Prologue– Dad (or Mom), is Java a
functional language?
– Don't you know your dad from your mom?!
3
3Wednesday, October 3, 12
What is FP like?
4Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌
5Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌1946
5Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌1946
5Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌1946 1956
5Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌1946 1956
John Backus
5Wednesday, October 3, 12
5
Alonzo Church
1936
𝛌1946 19761956
John Backus
Can Programming be Liberated from the von Neumann Style?
5Wednesday, October 3, 12
6
6Wednesday, October 3, 12
– Dad, what's good about FP?
6
6Wednesday, October 3, 12
– Dad, what's good about FP?
– It makes you look smart
6
6Wednesday, October 3, 12
– Dad, what's good about FP?
– It makes you look smart
– Like wearing glasses?
6
6Wednesday, October 3, 12
Effects (Mutability)
7
John von Neumann
State
com
man
ds
𝛌
f(g(x), y)VS
Inputs
Outputs
7Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
8Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
8Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
Are you functional?
Groovy
Scala
Java 8
Kotlin
Recursion
V
V
V
V
8Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
8Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
8Wednesday, October 3, 12
1, 1, 2, 3, 5, 8, 13, 21, 34, ...
Leonardo Fibonacci
State
com
man
ds
9Wednesday, October 3, 12
Effect-Free
10
10Wednesday, October 3, 12
Effect-Free
10
10Wednesday, October 3, 12
Effect-Free
– Dad, how do I
10
10Wednesday, October 3, 12
Effect-Free
– Dad, how do I
- print("Hello")?
10
10Wednesday, October 3, 12
Effect-Free
– Dad, how do I
- print("Hello")?
- write to a file?
10
10Wednesday, October 3, 12
Effect-Free
– Dad, how do I
- print("Hello")?
- write to a file?
- do both?
10
10Wednesday, October 3, 12
Effect-Free
– Dad, how do I
- print("Hello")?
- write to a file?
- do both?
10
Are you functional?
Groovy
Scala
Java 8
Kotlin
Recursion
V
V
V
V
X
X
Pure
X
X
10Wednesday, October 3, 12
Summary
• FP makes things simpler
• Sometimes at a huge price
• Our languages are not purely functional
11
11Wednesday, October 3, 12
Higher OrderFP brings order :)
12Wednesday, October 3, 12
FibonacciTest
13
13Wednesday, October 3, 12
FibonacciTest
13
– How do I test both implementations?
13Wednesday, October 3, 12
test(f)
14
14Wednesday, October 3, 12
test(f)
14
Are you functional?
Groovy
Scala
Java 8
Kotlin
Recursion
V
V
V
V
X
X
Pure
X
X
V
V
V
V
HO
14Wednesday, October 3, 12
GoF and FP
15
Strategy
Command Observer AbstractFactory
State Visitor
= Higher-Order
Function
15Wednesday, October 3, 12
Internal Iteration
16
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
users: ParallelCollection
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
users: ParallelCollection
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
users: ParallelCollection
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
users: ParallelCollection
16Wednesday, October 3, 12
Internal Iteration
16
users: ArrayList
user 1
user 2
user 3
user 4
Hello
Hello
Hello
Hello
users: ParallelCollection
16Wednesday, October 3, 12
Summary
• Good old callbacks/strategies
• Very important abstraction
17
17Wednesday, October 3, 12
ADTWhat is your "A" for?
18Wednesday, October 3, 12
Example: Messages
19
Server Client
19Wednesday, October 3, 12
Example: Messages
19
Server Clientsearch for "lambda"
19Wednesday, October 3, 12
Example: Messages
19
Server Clientsearch for "lambda"
exact match at ...
19Wednesday, October 3, 12
Example: Messages
19
Server Clientsearch for "lambda"
exact match at ...
similarity at ...
19Wednesday, October 3, 12
Example: Messages
19
message ::= search for term | exact item | similar item
Server Clientsearch for "lambda"
exact match at ...
similarity at ...
19Wednesday, October 3, 12
20
ADT
Algebraicdata type
Abstractdata type
~ Interface
~ Data class
20Wednesday, October 3, 12
20
ADT
Algebraicdata type
Abstractdata type
~ Interface
~ Data class
Are you functional?
Groovy
Scala
Java 8
Kotlin
Recursion
V
V
V
V
X
X
Pure
X
X
V
V
V
V
HO
V
V
V
V
ADT
20Wednesday, October 3, 12
ADT in Kotlin
21
21Wednesday, October 3, 12
UtilizationYou may have your cake, but can you eat it too?
22Wednesday, October 3, 12
Up to 5 HO-functions for free!
Upgrade
for
more
23Wednesday, October 3, 12
Static Utility Methods
24
backwards!
24Wednesday, October 3, 12
Static Utility Methods
24
backwards!
as opposed to
24Wednesday, October 3, 12
Extension Functions
25
25Wednesday, October 3, 12
Extension Functions
25
Receiver Type
25Wednesday, October 3, 12
Extension Functions
25
Receiver Type
receiver
25Wednesday, October 3, 12
Summary
• Extending existing types
• Without changing the classes
26
26Wednesday, October 3, 12
Epilogue
27Wednesday, October 3, 12
Epilogue– Dad, should I use FP?
27Wednesday, October 3, 12
Epilogue– Dad, should I use FP?
– What is your problem?!
27Wednesday, October 3, 12
Epilogue– Dad, should I use FP?
– What is your problem?!
P.S. Kotlin is cool :) http://kotlin.jetbrains.org27Wednesday, October 3, 12
Kotlin Resources
• Docs: http://kotlin.jetbrains.org
• Demo: http://kotlin-demo.jetbrains.com
• Code: http://github.com/jetbrains/kotlin
• Twitter:➡ @project_kotlin
➡ @abreslav
28
28Wednesday, October 3, 12
Recommended