The assignment for Functional Brighton Meet up was to describe what functional programming means to you...

1. Three things I’ve
noticed about
functional programming
while using Scala.

2. What have we have? What do we want?
happy birthday to
happy birthday to me
me #lol #omg
oops #lol oops #lol #omg
⋮ ⋮

3. What have we have? What do we want?
#lol, #omg
Some text
& some text

4. What have we have? What do we want?
#lol, #omg
Some text
& some text
List[String], String String

5. def appendTags(tweet: String, tags: List[String]) =
tags.foldLeft(tweet) { appendOne }
def appendOne(tweet: String, tag: String) =
if (tweet contains tag) tweet else tweet+" "+tag

6. StringBuffer b = new StringBuffer(tweet);
if (tags != null) {
for(String tag: tags) {
if (tag != null && b.indexOf(tag) == -1) {
b.append(tag).append(“ ”);
}
}
}
return b.toString();

7. “It’s the mutable
state, stupid.”
– Göetz et al.

8. val results =
List(yahoo _, google _).par.map(_.apply)

9. import scala.actors.Futures._
val results = List(yahoo _, google _) map (
f future{ f() } ) map (_.apply)

10. Option, for comprehensions,
flatMap & pattern matching are
astonishingly useful every day
and I’d never heard of them
before learning Scala.

11. for (int i = 0; i < resultFeed.getEntries().size(); i++) {
ContactEntry entry = resultFeed.getEntries().get(i);
if (entry.hasName()) {
Name name = entry.getName();
if (name.hasFullName()) {
...

12. for { entry ← resultFeed.getEntries
name ← Option(entry.getName)
full_name ← Option(name.getFullName)
birthday ← Option(entry.getBirthday)
} yield "%s: %s".format(full_name.getValue, when)

13. Summary
1. Thinking in terms of A B
2. Concurrency
3. Option (& friends) change everything