Mirah is a small, fast JVM language that uses Ruby syntax but compiles to Java bytecode. It was created by Charles Oliver Nutter, the creator of JRuby, who wanted to write Java code using a language as expressive as Ruby. Mirah has Ruby's syntactic sugar but is statically typed and compiled like Java, without runtime modification. It uses type inference and macros to provide Ruby-like conveniences while compiling to a small footprint without needing a runtime library, making it suitable for mobile applications. Developers can get started with Mirah by installing it with RVM and writing code that looks like Ruby but compiles to Java classes.

2. Mirah

3. What’s Mirah?

4. It’s a small, fast,
JVM language that uses
Ruby syntax.

5. How’d it come about?

6. Charles Oliver Nutter,
JRuby guy

7. Wanted to write
Java code in Ruby

8. Wanted to write
Java code in Ruby

9. Wanted to write Java
code in a language as
expressive as Ruby.

10. Expressive as Ruby?

11. http://www.flickr.com/photos/caroslines/513429518/

12. Syntactic Sugar
• Optional Arguments
• Internal Iteration(each, map, etc)
• Closures
• Literals
• String Interpretation

13. Mirah's got the sugar.

14. How Mirah Differs
from Ruby

15. 1. It’s statically typed
and compiled

16. Basically,
No Runtime
Object/Class
Modification

17. 2. It uses Java’s type
system

18. It has slightly different
semantics than Ruby's

19. e.g.,
Mirah has interfaces

20. So, what’s it look like?

21. Fibonacci
Example

22. Ruby
def fib(a)
if a < 2
a
else
fib(a - 1) + fib(a - 2)
end
end

23. Mirah
github.com/mirah/mirah/examples/fib.mirah
def fib(a:int):int
if a < 2
a
else
fib(a - 1) + fib(a - 2)
end
end

24. See what I did there?

25. def fib(a:int):int

26. def fib(a:int):int

27. Ruby Syntax
+ Java Types
- Runtime Modification

28. Other Super Powers

29. Type Inference
&
Macros

30. Type Inference?

31. Java
class Foo {
private int bar;
Foo() {
bar = 1;
}
public int bar() {
return bar;
}
}

33. Ruby
class Foo
def initialize
@bar = 1
end
def bar
@bar
end
end

34. Mirah
class Foo
def initialize
@bar = 1
end
def bar
@bar
end
end

35. @bar is inferred to be
an Integer

36. Mirah
class Foo
def initialize
@bar = 1
end
def bar
@bar
end
end

37. Java
class Foo {
private int bar;
Foo() {
bar = 1;
}
public int bar() {
return bar;
}
}

38. Mirah Java
// Generated from foo.mirah
public class Foo extends java.lang.Object
private int bar;
public Foo() {
this.bar = 1;
}
public int bar() {
return this.bar;
}
}

39. Ruby Syntax
+ Java Types
- Runtime Modification
+ Type Inference

40. Macros

41. For Convenience &
Awesomeness.

42. Used by the compiler

43. For example,

44. puts
=>
System.out.println();

45. Macros:
How each, map, ==, etc
are implemented

46. Macro Basics

47. say you have code like:
logger.debug(
"this #{takes_too_much_time}"
)

48. run
takes_too_much_time
in production?

49. No,
it takes too much time.

50. Macros to the rescue

51. macro def debug debug_input
quote do
if logger.debugEnabled
logger.debug `debug_input`
end
end
end

52. macro def debug debug_input
quote do
if logger.debugEnabled
logger.debug `debug_input`
end
end
end

53. macro def debug debug_input
quote do
if logger.debugEnabled
logger.debug `debug_input`
end
end
end

54. macro def debug debug_input
quote do
if logger.debugEnabled
logger.debug `debug_input`
end
end
end

55. macro def debug debug_input
quote do
if logger.debugEnabled
logger.debug `debug_input`
end
end
end

56. debug(
"this #{takes_too_much_time}"
)

58. if logger.debugEnabled
logger.debug(
"this #takes_too_much_time}"
)
end

59. debug(
"this #{takes_too_much_time}"
)

60. So, Macros are nifty

61. Ruby Syntax
+ Java Types
- Runtime Modification
+ Type Inference
+ Macros

62. Oh, there's another
thing.

63. No Runtime Library

64. You can do this:
$ mirahc -e "puts 'hello BRG'"
$ java -classpath . DashE.class

65. No Runtime
==
Small compiled
footprint

66. Small Footprint
==
good for mobile

67. For example,
see Pindah

68. Ruby Syntax
+ Java Types
- Runtime Modification
+ Type Inference
+ Macros
- Runtime Library

70. Get Started
$ rvm jruby
$ gem install mirah
$ mirah -e "puts 'hello world'

71. Mirah projects to check out:
• Dubious - Rails-like web framework for
Google App Engine
• Pindah - Android App framework

72. I'm Nick
@baroquebobcat

73. I work at

74. We're Hiring.
gnip.com/jobs

75. A couple links
mirah.org
github.com/mirah

76. Questions?