Crystal is a pl created in 2014 by Ary Borenszweig.
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In computer software programming languages, Crystal is a general-purpose, object-oriented programming language, designed and developed by Ary Borenszweig and Juan Wajnerman and more than 200 contributors. With syntax inspired by the language Ruby, it is a compiled language with static type-checking, but specifying the types of variables or method arguments is generally unneeded. Types are resolved by an advanced global type inference algorithm. Read more on Wikipedia...
# Type your code here, or load an example.
# compile with --prelude=empty
fun square(num : Int32) : Int32
num &* num
end
puts "Hello, world!"
puts "Hello World"
# Hello world in Crystal
puts "Hello World"
#!/usr/bin/env bin/crystal --run
require "../../spec_helper"
describe "Type inference: declare var" do
it "types declare var" do
assert_type("a :: Int32") { int32 }
end
it "types declare var and reads it" do
assert_type("a :: Int32; a") { int32 }
end
it "types declare var and changes its type" do
assert_type("a :: Int32; while 1 == 2; a = 'a'; end; a") { union_of(int32, char) }
end
it "declares instance var which appears in initialize" do
result = assert_type("
class Foo
@x :: Int32
end
Foo.new") { types["Foo"] }
mod = result.program
foo = mod.types["Foo"] as NonGenericClassType
foo.instance_vars["@x"].type.should eq(mod.int32)
end
it "declares instance var of generic class" do
result = assert_type("
class Foo(T)
@x :: T
end
Foo(Int32).new") do
foo = types["Foo"] as GenericClassType
foo_i32 = foo.instantiate([int32] of Type | ASTNode)
foo_i32.lookup_instance_var("@x").type.should eq(int32)
foo_i32
end
end
it "declares instance var of generic class after reopen" do
result = assert_type("
class Foo(T)
end
f = Foo(Int32).new
class Foo(T)
@x :: T
end
f") do
foo = types["Foo"] as GenericClassType
foo_i32 = foo.instantiate([int32] of Type | ASTNode)
foo_i32.lookup_instance_var("@x").type.should eq(int32)
foo_i32
end
end
it "declares an instance variable in initialize" do
assert_type("
class Foo
def initialize
@x :: Int32
end
def x
@x
end
end
Foo.new.x
") { int32 }
end
end
channel = Channel(Int32).new
spawn do
puts "Before first send"
channel.send(1)
puts "Before second send"
channel.send(2)
end
puts "Before first receive"
value = channel.receive
puts value # => 1
puts "Before second receive"
value = channel.receive
puts value # => 2
abstract do if nil? self unless alias else in of sizeof until as elsif include out struct when as? end instance_sizeof pointerof super while asm ensure is_a? private then with begin enum lib protected true yield break extend macro require type case false module rescue typeof class for next return uninitialized def fun nil select union