crystal

books.txt

@@ -5,6 +5,7 @@ aws-lambda/aws.json,aws-lambda,
 bash/bash.json,bash,
 css/css.json,css,
 collab-dev/collab.json,collab-dev,
+crystal/crystal.json,crystal,
 data-science/data.json,data-science,
 dart/dart.json,dart,
 digitalocean/do.json,digitalocean,

crystal/Dockerfile

@@ -0,0 +1,3 @@
+FROM crystallang/crystal:latest
+WOR
+

crystal/crystal

@@ -0,0 +1 @@
+docker run --rm -it -w/opt -v$(pwd):/opt crystallang/crystal crystal $*

crystal/crystal.json

@@ -0,0 +1,12 @@
+{
+    "title": "Crystal Programming",
+    "author": "Gabor Szabo",
+    "description": "",
+    "first_year": "2021",
+    "copyright_name": "Gabor Szabo",
+    "copyright_url": "https://szabgab.com/",
+    "version": "0.01",
+    "files": [
+        "introduction.md"
+    ]
+}

crystal/examples/add_numbers.cr

@@ -0,0 +1,4 @@
+x = 23
+y = 19
+z = x + y
+puts z  # 42

crystal/examples/escaping.cr

@@ -0,0 +1,5 @@
+name = "Foo Bar"
+puts "Hello '#{name}'!"
+puts "Hello \"#{name}\"!"
+puts %(Hello "#{name}"!) # alternative quotes
+puts %{Hello "#{name}"!}

crystal/examples/hello_name.cr

@@ -0,0 +1,2 @@
+name = "Foo Bar"
+puts "Hello " + name + "!"

crystal/examples/hello_name_interpolation.cr

@@ -0,0 +1,2 @@
+name = "Foo Bar"
+puts "Hello #{name}!"

crystal/examples/hello_world.cr

@@ -0,0 +1 @@
+puts "Hello World!"

crystal/examples/math.cr

@@ -0,0 +1,3 @@
+p! Math::PI
+p! Math::TAU
+p! Math::E 

crystal/examples/math.out

@@ -0,0 +1,3 @@
+Math::PI # => 3.141592653589793
+Math::TAU # => 6.283185307179586
+Math::E # => 2.718281828459045

crystal/examples/number_methods.cr

@@ -0,0 +1,7 @@
+x = -5.2
+p! x.abs
+p! x.round
+# p! x.even? # Undefined method even? for Float64
+
+age  = 42
+p! age.even?

crystal/examples/types.cr

@@ -0,0 +1,11 @@
+name = "Foo Bar"
+puts typeof(name)  # String
+p! typeof(name)    # typeof(name) => String
+
+age = 42
+puts typeof(age)   # Int32
+p! typeof(age)     # typeof(age) => Int32
+
+pi = 3.14
+puts typeof(pi)   # Float64
+p! typeof(pi)     # typeof(pi) => Float64

crystal/introduction.md

@@ -0,0 +1,102 @@
+# Introduction
+{id: introduction}
+
+## Crystal Language
+{id: crystal-language}
+
+* [Crystal lang](https://crystal-lang.org/)
+* Similar to Ruby
+
+
+## Docker on Linux
+{id: docker-on-linux}
+
+* [Docker Crystal](https://hub.docker.com/r/crystallang/crystal)
+* Install Docker
+* Create a file called `crystal` with the following content:
+
+![](crystal)
+
+* Make it executable by running `chmod +x crystal`
+* Run `./crystal examples/hello_world.cr`
+
+## Hello World (puts)
+{id: hello-world}
+{i: puts}
+
+![](examples/hello_world.cr)
+
+* `puts` stands for "put string"
+
+
+## Hello Name (variables)
+{id: hello-name}
+
+![](examples/hello_name.cr)
+
+## Hello Name with interpolation
+{id: hello-name-interpolation}
+
+![](examples/hello_name_interpolation.cr)
+
+## Escaping - Alternative delimiters
+{id: escaping}
+
+![](examples/escaping.cr)
+
+
+## Add numbers
+{id: add-numbers}
+
+![](examples/add_numbers.cr)
+
+## Types
+{id: types}
+{i: String}
+{i: Int32}
+{i: Float64}
+{i: p!}
+
+![](examples/types.cr)
+
+
+## Numeric Operators
+{id: numeric-operators}
+
+
+```
++
+-
+*
+** (exponent)
+/
+// (floor division)
+% (modulus)
+```
+
+## Comparision Operators
+{id: comparision-operators}
+
+* ==, <, > <=, >=
+
+* Spaceship operator <=> returns -1, 0, or 1
+
+
+## Math
+{id: math}
+
+![](examples/math.cr)
+![](examples/math.out)
+
+
+## Other
+{id: other}
+
+* Single quotes vs double quotes
+
+No type-checking?
+
+x = "one"
+x = 1
+p! x
+p! typeof(x)