add

crystal/README.md

@@ -1,16 +1,12 @@
 
 * Implement the exercises in the Python course
-* Code to parse the .md files and check if each one of the files from the examples directory has been used.
-* How to install 3rd party modules?
-* List of 3rd party modules
 * Create a web application
 
 * Write a test for https://github.com/watzon/octokit.cr that will use a secret stored in GitHub Actions to use the API
 
 * Modules
 * Classes
 
-
 * Read shard.yml file in particular
 * Web application development?
 * Access to SQLite?

crystal/crystal.json

@@ -22,6 +22,7 @@
         "structs.md",
         "regexes.md",
         "testing.md",
+        "modules.md",
         "json.md",
         "range.md",
         "random.md",

crystal/examples/functions/splat.cr

@@ -0,0 +1,7 @@
+def sum(*numbers : Int32)
+  puts typeof(numbers) # Tuple(Int32, Int32, Int32)
+  numbers.sum
+end
+
+res = sum(2, 3, 4)
+puts res # 9

crystal/examples/modules/include.cr

@@ -0,0 +1,13 @@
+module Tools
+  def screwdriver
+    puts "Screwdriver"
+  end
+end
+
+class Device
+  include Tools
+end
+
+x = Device.new
+p! x
+x.screwdriver

crystal/examples/modules/namespace.cr

@@ -0,0 +1,7 @@
+module MyProject
+  class Device
+  end
+end
+
+x = MyProject::Device.new
+p! x

crystal/examples/other/enums.cr

@@ -0,0 +1,19 @@
+enum Direction : UInt8
+  Left
+  Right
+  Up
+  Down
+
+  def left?
+    self == Direction::Left
+  end
+end
+
+puts Direction::Left
+puts Direction::Left.value
+puts Direction::Right
+dir = Direction::Left
+puts dir.left?
+
+dir = Direction::Right
+puts dir.left?

crystal/examples/other/int_or_nil.cr

@@ -0,0 +1,11 @@
+text = "Black cat"
+idx = text.index("cat")
+puts typeof(idx) # (Int32 | Nil)
+
+# puts text[idx]
+# Error: no overload matches 'String#[]' with type (Int32 | Nil)
+
+if idx.is_a?(Int32)
+  puts typeof(idx) # Int32
+  puts text[idx]
+end

crystal/examples/other/proc.cr

@@ -0,0 +1,3 @@
+square = ->(x : Int32) { x * x }
+puts typeof(square) # Proc(Int32, Int32)
+puts square.call(3) # 9

crystal/examples/other/type_of_array_elements.cr

@@ -0,0 +1,15 @@
+values = [1, 2, "three", "four"]
+puts typeof(values)
+puts typeof(values[0])
+puts typeof(values[2])
+puts ""
+
+values.each { |val|
+  puts typeof(val)
+  # puts val.size
+  # Error: undefined method 'size' for Int32 (compile-time type is (Int32 | String))
+
+  if val.is_a?(String)
+    puts val.size
+  end
+}

crystal/functions.md

@@ -44,6 +44,11 @@
 
 ![](examples/functions/pass_array_instead_of_individual_values.cr)
 
+## Any number of arguments (splat, *)
+{id: any-number-of-arguments}
+
+![](examples/functions/splat.cr)
+
 ## Manually separate
 {id: manually-separate}
 

crystal/intro.md

@@ -13,14 +13,21 @@
 * Concurrency with green threads called fibers
 * C-bindings
 
-## Crystal Shards
+## Crystal Shards (3rd party libraries)
 {id: crystal-shards}
 {i: shards}
 
 * The 3rd party modules directory
+* [Shardbox](https://shardbox.org/)
 * [Crystal Shards](https://crystalshards.xyz/)
 * Use `shards init` to create a file called `shard.yml` and describe the dependencies there.
 
+## How to install 3rd party shards?
+{id: install-shards}
+
+* Create a file called `shard.yml` for your project listing the dependencies of this project
+* Run `shards install`
+
 ![](shard.yml)
 
 ## Install Crystal
@@ -291,3 +298,5 @@ echo %ERROR_LEVEL%
 {i: gets}
 
 ![](examples/intro/gets.cr)
+
+

crystal/modules.md

@@ -0,0 +1,13 @@
+# Modules
+{id: modules}
+
+## Namespace
+{id: namespace}
+
+![](examples/modules/namespace.cr)
+
+## Extend class - include module
+{id: include-module}
+
+![](examples/modules/include.cr)
+

crystal/other.md

@@ -195,6 +195,33 @@ require "some_name"         # Find it somewhere (standard library, src directory
 
 ![](examples/other/math.cr)
 
+## Proc
+{id: proc}
+{i: Proc}
+
+* [Proc](https://crystal-lang.org/api/Proc.html)
+
+![](examples/other/proc.cr)
+
+## Enums
+{id: enums}
+{i: enum}
+
+![](examples/other/enums.cr)
+
+## Type of array elements
+{id: type-of-array-elements}
+
+![](examples/other/type_of_array_elements.cr)
+
+All the elements of an array "inherit" the type from the array
+
+## Int32 or Nil
+{id: int32-or-nil}
+
+![](examples/other/int_or_nil.cr)
+
+
 ## Resources
 {id: resources}