My talk from Functional Vilnius MeetUp #6. http://www.functionalvilnius.lt/posts/2015-10-03-6th-meetup-announcement.html Golang is becoming more and more popular. Most likely many of you have heard of its upgraded garbage collector and possibilities to work with lightweight threads – goroutines. Obviously, Golang is quite a good choice for server-side software oriented on a huge load. As Scala backend developer, I am a big fan of functional programming and actor model. Golang seems very promising, but from the first glance, its a totally imperative language. In my speech I’m going to tell about my experiments with Golang and attempt to use it as a functional language.

1. Golang from
Scala
developer’s
perspective

2. About
me
Svetlana
Bozhko
Backend
Scala
Developer
@
Adform

3. The
goal
Is
Go
really
so
bad imperative?

4. Content
Short
intro
into
Go
Tooling
FP
vs.
Go
IMHO

5. Usage
https://github.com/golang/go/wiki/GoUsers

7. How
to
start?
http://tour.golang.org/
http://golangshow.com/

8. Go
Good
parts

9. Go
is
actually
a
pretty
simple
language!

10. Even
too
simple
for
2015

12. Advanced
GC

13. “Build
time
matters
more
than
anything
else”
-­‐ Rob
Pike

14. gofmt

15. Quite
good
tools
build-­‐in
(version,
get,
build,
…)
editors
(vim,
intellij,
sublime,
…)

16. Concurrency
• Channels
send
data
between
threads
easily,
asynchronously
or
synchronously
• GoRoutines
spin
up
another
thread,
just
like
that!

17. No
Language
Is
Perfect...

18. Go
Mentality
• Smallest
possible
feature
set
• It’s
okay
to
copy
some
code
• Productivity
instead
of
hyper-­‐elegant
code

19. Let’s
get
rid
of
• Implicit
numeric
conversion
(int !=
int32)
• ‘Implements’
keyword
• ‘Classes’
• Constructor/destructor
• Function
overloading
• Pointer
arithmetic
• Exceptions
and
try/catch
• Generics
• …

20. Strict
compiler
which
interrupts
you
sometimes

21. Wait,
Go
has
‘goto’?

22. Wait,
how
to
debug?
GDB,
but
it’s
not
very
good
way

23. Dependency
management
vendor
(since
1.5)

24. FP
vs.
Go

25. Wikipedia:
“Functional
programming is
a programming
paradigm
— a
style
of
building
the
structure
and
elements
of
computer
programs
— that
treats computation as
the
evaluation
of mathematical
functions and
avoids
changing-­‐state and mutable data.”

26. What
it
means?
No
mutable
data
(no
side
effect)
No
mutable
state
(no
implicit,
hidden
state)
Same
result
returned
by
functions
called
with
the
same
inputs
Functions
are
pure
functions
in
the
mathematical
sense

27. Advantages?
Cleaner
code
Referential
transparency

28. Referential
transparency
Memoization
Cache
results
Idempotence
Modularization
We
have
no
state
Ease
of
debugging
Functions
are
isolated
and
very
easy
to
debug

29. Referential
transparency
Parallelization
Functions
calls
are
independent
We
can
parallelize
in
different
process/CPUs/computers/...
res
=
func1(a,
b)
+
func2(a,
c)

30. Referential
transparency
With
no
shared
data,
concurrencygets
a
lot
simpler:
No
semaphores
No
monitors
No
locks
No
race-­‐conditions
No
dead-­‐locks

31. Nonetheless
Golang has
built-­‐in
“sync”
package
with
mutexes

32. Don’t
Update,
Create!

33. String

34. Arrays

35. Maps

36. Higher
order
functions

37. FP
libraries
https://github.com/yanatan16/itertools
https://github.com/tobyhede/go-­‐underscore

38. Higher
order
functions

39. Map

40. Filter

41. Reduce

42. Closures

43. Currying
and
Partial
Functions

44. Eager
vs
Lazy
Evaluation
Golang channels
and
goroutines enable
the
creation
of
generators
that
could
be
a
way
to
have
lazy
evaluation

45. Recursion

46. FP
&
OOP
It
is
possible
do
FP
in
OOP?
Yes
it
is!
OOP
is
orthogonal
to
FP.
At
least
in
theory…

47. Exercise!
What
is
the
sum
of
the
first
10
natural
number
whose
square
value
is
divisible
by
2?

48. Exercise!
Imperative Functional

49. Learn
at
least
one
functional
language
It
will
open
your
mind
to
a
new
paradigm
becoming
you
a
better
programmer

50. Conclusion
Technologies
are
awesome!
The
problem
is
people how
we
use
them.

51. Thank
you!
Questions?
Svetlana
Bozhko aka
@SBozhko
http://devzen.ru/
svt.bozhko@gmail.com

52. Links
https://golang-­‐ru.slack.com/messages
https://www.youtube.com/watch?list=PLPHSBhlVt
TyfwIKn7r_a5xkzzMu-­‐iey-­‐w&v=cGXorQkw3JE