Intro to Crystal Language

What is Crystal Language?

Talk presented online at RubyConfOnline December 2015.

Transcript

1. Crystal Language https://crystal-lang.org
2. Luis Lavena Work: area17.com Twitter: @luislavena GitHub: luislavena
3. What if Ruby was created today?
4. Overview of features • LLVM-backend • Ruby-like syntax • Compiles to native code • Global type inference • Compile time error checking • Go-inspired concurrency design*
5. LLVM-backend • Used by many new languages (ie. Rust, Swift) • Simplifies architecture porting and cross compilation • Advanced branching and native code optimizations • Stands on the shoulders of giants
6. Ruby-like syntax • Reduces learning curve • Inspired but not directly copied • many ways to do things vs one way (no aliases) • Compiled, no VM or bytecode to interpret • No eval or crazy meta-programming • Self-hosted (Crystal is written in Crystal)
7. Ruby-like syntax, on steroids • Initializer shortcuts • Method overloading • Macros • Generics • 21st century Standard Library
8. Initializer shortcuts # Ruby class Greeter def initialize(entity) @entity = entity end end # Crystal class Greeter def initialize(@entity) end end
9. Method overload # Ruby def guess(value) case value when Integer puts "Integer!" when String puts "String!" else puts "No idea!" end end # Ruby guess 10 # => "Integer!" guess "hello!" # => "String!" guess true # => "No idea!"
10. Method overload # Crystal def guess(value : Int32) puts "Integer!" end def guess(value : String) puts "String!" end def guess(value) puts "No idea!" end # Crystal guess 10 # => "Integer!" guess "hello!" # => "String!" guess true # => "No idea!"
11. Macros • Executed before type inference • Transform AST at compilation time • Used for minimal meta-programming and callbacks ◦ inherited (Class) ◦ included (Module) ◦ method_missing ◦ delegate ◦ setter/getter/property ◦ respond_to?
12. Macros (expanded) class Person getter name end class Person def name @name end end
13. Type inference • Always know what is being used and where • Compile time checks beats runtime errors ;-)
14. Types • String is not the same as Char ◦ “a” vs ‘a’ • Int32 and Int64 • Float32 and Float64 • Nil • Boolean • Array of types (Array(T))
15. Types a = [1, 2, 3].map { |x| x + 3 } pp a # => a = [4, 5, 6] pp typeof(a) # => Array(Int32) b = [1, "a", 'b'] pp typeof(b) # => Array(String | Int32 | Char) # b << 12.5 # => Compile error (Float32)
16. Modern Standard Library • No legacy libraries ;-) • HTTP Client and Servers built-in • OAuth2 and Websockets • YAML, JSON, XML, Markdown parsers • Growing ecosystem (shards)
17. HTTP Server require "http/server" server = HTTP::Server.new(9292) do |request| HTTP::Response.ok "text/plain", "Hello world!" end puts "Listening on http://0.0.0.0:9292" server.listen
18. HTTP Server $ crystal build --release http_server.cr $ ./http_server Listening on http://0.0.0.0:9292
19. HTTP Server (benchmark: wrk) $ ./wrk -c 10 -t 2 http://localhost:9292/ Running 10s test @ http://localhost:9292/ 2 threads and 10 connections Thread Stats Avg Stdev Max +/- Stdev Latency 97.90us 212.99us 13.47ms 99.67% Req/Sec 55.93k 4.88k 112.00k 90.55% 1118367 requests in 10.10s, 107.72MB read Requests/sec: 110733.34 Transfer/sec: 10.67MB
20. HTTP Server (prefork) require "http/server" server = HTTP::Server.new(9292) do |request| HTTP::Response.ok "text/plain", "Hello world!" end puts "Listening on http://0.0.0.0:9292" server.listen_fork(3)
21. HTTP Server (benchmark: wrk) $ ./wrk -c 10 -t 2 http://localhost:9292/ Running 10s test @ http://localhost:9292/ 2 threads and 10 connections Thread Stats Avg Stdev Max +/- Stdev Latency 128.90us 525.80us 12.09ms 97.18% Req/Sec 87.02k 17.70k 117.77k 63.50% 1731802 requests in 10.01s, 166.81MB read Requests/sec: 173042.01 Transfer/sec: 16.67MB
22. HTTP Server (memory) # fresh $ pmap -x $(http_server PID) Address Kbytes RSS Dirty total kB 69772 4408 776 total kB 111224 5116 1316 total kB 70264 4956 1156 Start wrk GC
23. HTTP Client require "http/client" response = HTTP::Client.get "http://www.example.com" response.status_code # => 200 response.body.lines.first # => "<!doctype html>"
24. JSON Parsing (schema) require "json" class Person JSON.mapping({ name: String, age: Int32, }) end
25. JSON Parsing data = %([{"name":"Luis","age":36},{"name":"Ana","age":21}]) Array(Person).from_json(data).each do |person| if person.age > 30 puts "Getting old, #{person.name}?" end end
26. JSON Parsing class Person # … mapping … def initialize(@name, @age) end end user = Person.new("Aaron", 34) user.to_json # => {"name":"Aaron","age":34}
27. https://github.com/kostya/benchmarks#json
28. Ecosystem (shards) • Bundler-like • Decentralized • Git-based • shard.yml & shard.lock
29. Awesome, does it run Rails?
30. No
31. No
32. Web frameworks • Amethyst • Kemal • Moonshine • Carbon • Chocolate • Beryl* https://github.com/veelenga/awesome-crystal
33. Simplified deployment • Single executable • Small footprint and size • Fast compile times • Easy Heroku deploy* https://github.com/scaint/heroku-buildpack-crystal
34. Community • Small, friendly • Code of Conduct • New language, fewer libraries • 3rd party libraries starting to show • Less drama ;-) https://github.com/veelenga/awesome-crystal
35. Useful resources • Docs: http://crystal-lang.org/docs/ • API: http://crystal-lang.org/api/ • Group: https://groups.google.com/group/crystal-lang • Twitter: https://twitter.com/CrystalLanguage • Awesome: https://github.com/veelenga/awesome-crystal
36. Thanks! github.com/luislavena