1. 1. Crystal
2. 2. Introduction
3. 1. 2.1. Crystal Language
   2. 2.2. Crystal Shards (3rd party libraries)
   3. 2.3. How to install 3rd party shards?
   4. 2.4. Install Crystal
   5. 2.5. Crystal in Docker on Linux
   6. 2.6. Hello World (puts)
   7. 2.7. Run Crystal source code
   8. 2.8. Compile Crystal to executable
   9. 2.9. Speed of Crystal
   10. 2.10. Hello World (print)
   11. 2.11. Hello Name (variables)
   12. 2.12. Hello Name with interpolation
   13. 2.13. Interpolation
   14. 2.14. Escaping - Alternative quote as delimiters
   15. 2.15. Debugging print p!
   16. 2.16. Comments
   17. 2.17. Code formatting
   18. 2.18. Types - typeof
   19. 2.19. Compound Types - typeof
   20. 2.20. Add numbers - concatenate strings
   21. 2.21. Add mixed strings and Integers
   22. 2.22. Numeric Operators
   23. 2.23. Methods of Int32
   24. 2.24. Methods of Float64
   25. 2.25. Program name
   26. 2.26. Command line arguments - ARGV
   27. 2.27. Early exit
   28. 2.28. Rectangle
   29. 2.29. True values
   30. 2.30. Math - PI
   31. 2.31. Read from STDIN
   32. 2.32. Read number from STDIN
   33. 2.33. Interactive environments
   34. 2.34. Crystal one-liners
   35. 2.35. Crystal and random numbers
   36. 2.36. Exercise: Hello World
   37. 2.37. Exercise: Hello Name - STDIN
   38. 2.38. Exercise: Hello Name - ARGV
   39. 2.39. Exercise: Circle STDIN
   40. 2.40. Exercise: Circle ARGV
   41. 2.41. Exercise: Calculator STDIN
   42. 2.42. Exercise: Calculator ARGV
   43. 2.43. Exercise: Age limit
4. 3. Strings
5. 1. 3.1. Strings intro
   2. 3.2. Length or size of a string
   3. 3.3. Locate substring (index, rindex)
   4. 3.4. Reverse a string
   5. 3.5. Substring, range of characters
   6. 3.6. String includes another string
   7. 3.7. String starts with
   8. 3.8. String ends with
   9. 3.9. Replace part of a string (substitute)
   10. 3.10. Is the string empty or blank?
   11. 3.11. Iterate over characters of a string
   12. 3.12. Type conversion from string to float, to int
   13. 3.13. Converting string to integer or float
   14. 3.14. Split String
   15. 3.15. String Transliteration
   16. 3.16. String Builder
   17. 3.17. sprintf and %
   18. 3.18. Split to the same string length
   19. 3.19. Split characters
   20. 3.20. printf
   21. 3.21. Here documents
6. 4. Conditionals
7. 1. 4.1. Comparison Operators
   2. 4.2. Spaceship operator
   3. 4.3. if statement
   4. 4.4. elsif
   5. 4.5. unless statement
   6. 4.6. Suffix if
   7. 4.7. Suffix unless
   8. 4.8. Logical operators
   9. 4.9. Truth-table
   10. 4.10. case / when
   11. 4.11. case of types
   12. 4.12. Ternary operator and or to set default value
   13. 4.13. Exercise: Number Guessing game - level 0
   14. 4.14. Solution: Number Guessing game - level 0
8. 5. Loops
9. 1. 5.1. loop
   2. 5.2. loop controls (next, break)
   3. 5.3. while
   4. 5.4. until
   5. 5.5. Exercise: Number guessing game
   6. 5.6. Solution: Number guessing game
10. 6. Arrays
11. 1. 6.1. Arrays intro
    2. 6.2. Array elements - indexing
    3. 6.3. Array iterate over (each, each_with_index)
    4. 6.4. Array push, append, <<
    5. 6.5. Empty array
    6. 6.6. Count digits
    7. 6.7. Operations on arrays
    8. 6.8. Add arrays
    9. 6.9. Repeat arrays
    10. 6.10. Select (filter, grep)
    11. 6.11. Reject (negative filter, grep)
    12. 6.12. Transform with map
    13. 6.13. Sample from array
    14. 6.14. Shuffle array
    15. 6.15. join
    16. 6.16. Remove nil elements
    17. 6.17. Create Array with nil
    18. 6.18. Does array include a value
    19. 6.19. Delete element from array by value
    20. 6.20. Delete element from array by location
    21. 6.21. Insert element into array at location
    22. 6.22. Arrays shift - remove first element
    23. 6.23. Arrays uniq elements
    24. 6.24. First element of the array
    25. 6.25. Permutations
12. 7. Hash
13. 1. 7.1. Hash intro
    2. 7.2. Count words
    3. 7.3. Create empty hash
    4. 7.4. Hash and types
    5. 7.5. Hash get value, get default value
    6. 7.6. Merge hashes
    7. 7.7. Delete - remove an element from a hash
    8. 7.8. Reject - remove an element from a hash
    9. 7.9. Clear - empty a hash
    10. 7.10. Select - keep certain key-value pairs
    11. 7.11. Multi-dimensional hash
    12. 7.12. Dig a hash
14. 8. Files
15. 1. 8.1. Files intro
    2. 8.2. Read from file (slurp)
    3. 8.3. Read lines into array
    4. 8.4. Read file line-by-line
    5. 8.5. Write to file
    6. 8.6. Append to file
    7. 8.7. Does file exist?
    8. 8.8. Size of file?
    9. 8.9. Last Modified date of file?
    10. 8.10. Counter
    11. 8.11. Multi Counter JSON
    12. 8.12. Multi Counter YAML
16. 9. Directories
17. 1. 9.1. List directory content
    2. 9.2. List directory tree
    3. 9.3. Get Current working directory (cwd, pwd)
    4. 9.4. Temporary directory
    5. 9.5. Tempdir function
    6. 9.6. Join / concatenate file system path
    7. 9.7. Join / concatenate file system path
    8. 9.8. Path from string
    9. 9.9. Expand Path
18. 10. Sets
19. 1. 10.1. Create empty set
    2. 10.2. Set examples
20. 11. Functions
21. 1. 11.1. Functions and methods
    2. 11.2. Function return value
    3. 11.3. Function parameter passing
    4. 11.4. Function parameter default value
    5. 11.5. Wrong number of arguments
    6. 11.6. Any number of arguments (splat, *)
    7. 11.7. Manually separate
    8. 11.8. Tuple from
    9. 11.9. Array overload
    10. 11.10. Multiple dispatch
    11. 11.11. Implicit return value
    12. 11.12. Return Type definition
    13. 11.13. Type or Nil
    14. 11.14. Yield
    15. 11.15. Yield with parameters
    16. 11.16. Block and parameters
22. 12. Tuples and Named Tuples
23. 1. 12.1. Create Tuple
    2. 12.2. Create Named Tuple
    3. 12.3. Access fields of Named Tuple
    4. 12.4. Named Tuple with non-alphanumeric fields
    5. 12.5. Named Tuple with optional field
24. 13. Structs
25. 1. 13.1. Empty struct
    2. 13.2. Initialize immutable struct
    3. 13.3. Initialize immutable struct - shorthand
    4. 13.4. Immutable struct with getters
    5. 13.5. Immutable struct with getter macro
    6. 13.6. Mutable Struct with setter
    7. 13.7. Mutable Struct with property macro
    8. 13.8. Struct with optional attributes
    9. 13.9. Struct with default value
    10. 13.10. Struct pass-by-value
    11. 13.11. Struct from JSON
    12. 13.12. Struct from JSON - upper case
    13. 13.13. Struct both from JSON and initialize
    14. 13.14. Struct from JSON - manual parsing
    15. 13.15. Multi-level struct manually
    16. 13.16. Multi-level struct from JSON
    17. 13.17. Struct from JSON with extra data
    18. 13.18. Struct from JSON missing data (optional fields)
    19. 13.19. Extend struct
    20. 13.20. Extend other structs
26. 14. Classes
27. 1. 14.1. Empty Class definition
    2. 14.2. Class with attributes
    3. 14.3. Class with getters
    4. 14.4. Class with setter
    5. 14.5. Class with getters and setter (property)
    6. 14.6. Class with property with default value
    7. 14.7. Class with declared getter and default value
    8. 14.8. Class with declared getter
    9. 14.9. Serialize Crystal-lang class to/from JSON from_json to_json
    10. 14.10. Compare objects for equality
    11. 14.11. Singleton using class properties
    12. 14.12. Singleton using class properties with default values
    13. 14.13. Class monkey-path add method
    14. 14.14. Stringification to_s
28. 15. Regexes
29. 1. 15.1. Alternate delimiter matching slashes
    2. 15.2. Substitute
    3. 15.3. gsub
30. 16. Testing
31. 1. 16.1. Testing 1
    2. 16.2. Testing with Spec
32. 17. Modules
33. 1. 17.1. Namespace
    2. 17.2. Extend class - include module
34. 18. JSON
35. 1. 18.1. JSON (to_json, parse)
    2. 18.2. JSON to NamedTuple
    3. 18.3. Reading a JSON file
    4. 18.4. JSON to Array
36. 19. Range
37. 1. 19.1. Range using dots
    2. 19.2. Range using a class
    3. 19.3. Range - sum
    4. 19.4. Range - count
    5. 19.5. Range and loop controls
    6. 19.6. Range with step
    7. 19.7. Range to Array
38. 20. Random
39. 1. 20.1. rand
    2. 20.2. Random in other parts of Crystal
    3. 20.3. Random as a class
    4. 20.4. Random - seed
40. 21. YAML
41. 1. 21.1. Parse YAML
42. 22. Exception Handling in Crystal-lang
43. 1. 22.1. Catch exception - begin, rescue
    2. 22.2. Raise exception
44. 23. Logging
45. 1. 23.1. Crystal logging
46. 24. SQLite
47. 1. 24.1. Try SQLite
    2. 24.2. Multi-counter with SQLite
    3. 24.3. SQLite last_id last_insert_id
    4. 24.4. SQLite UPDATE row_affected
    5. 24.5. SQLite exception handling (during INSERT)
    6. 24.6. SQLite all
    7. 24.7. SQLite in memory
48. 25. Time
49. 1. 25.1. Dates and Time
    2. 25.2. Sleep
    3. 25.3. Time difference or Time::Span
    4. 25.4. Elapsed time
    5. 25.5. Timestamp formatting
    6. 25.6. Add timespan
    7. 25.7. Time Types
50. 26. CLI
51. 1. 26.1. ARGV
    2. 26.2. Usage statement and exit
    3. 26.3. Command line Option Parser (argparse, GetOpts)
    4. 26.4. Pass parameters to OptionParser
    5. 26.5. Order of parsing
52. 27. HTTP Client
53. 1. 27.1. HTTP Client example
    2. 27.2. Parse URL (URI)
    3. 27.3. HTTP::Request GET
    4. 27.4. HTTP::Request POST
54. 28. Process
55. 1. 28.1. Execute external program (system)
    2. 28.2. Execute external program (backtick)
    3. 28.3. Execute external program (Process)
    4. 28.4. Execute external program (capture)
    5. 28.5. Execute external program (capture)
    6. 28.6. Abort
56. 29. Concurrency
57. 1. 29.1. Send and receive
    2. 29.2. Concurrent HTTP request
58. 30. Kemal
59. 1. 30.1. About Kemal
    2. 30.2. Kemal Install
    3. 30.3. Hello World
    4. 30.4. Testing Hello World
    5. 30.5. Kemal Autorestart (autoreload)
    6. 30.6. Kemal GET parameters
    7. 30.7. Kemal POST parameters
    8. 30.8. Kemal Route parameters
    9. 30.9. Kemal ECR Templates
    10. 30.10. Kemal with Jinja templates
    11. 30.11. Kemal Elapsed time
    12. 30.12. Accept GET, POST, and route parameter in the same POST route
    13. 30.13. Kemal indicate 404
    14. 30.14. Kemal Styling 404 pages
    15. 30.15. Kemal set headers (change content-type)
    16. 30.16. Kemal redirect
    17. 30.17. Kemal in Docker
60. 31. Other
61. 1. 31.1. Sequence
    2. 31.2. Check if variable is nil?
    3. 31.3. Single quotes vs double quotes
    4. 31.4. No type-checking?
    5. 31.5. Divide by zero is Infinity
    6. 31.6. Require other files
    7. 31.7. List Methods
    8. 31.8. Checking the slides
    9. 31.9. Crystal mine
    10. 31.10. Ameba Linter
    11. 31.11. Gravatar
    12. 31.12. Try Crystal
    13. 31.13. STDERR, STDOUT
    14. 31.14. Return Boolean
    15. 31.15. Symbols
    16. 31.16. Docspec
    17. 31.17. require
    18. 31.18. Constants
    19. 31.19. Multiple assignment
    20. 31.20. Chained assignment
    21. 31.21. Int methods: Times
    22. 31.22. Int64 Zero
    23. 31.23. Question mark: ?
    24. 31.24. Exclamation mark: !
    25. 31.25. Ampersand: &
    26. 31.26. STDIN don't accept nil
    27. 31.27. Math
    28. 31.28. Proc
    29. 31.29. Enums
    30. 31.30. Type of array elements
    31. 31.31. Environment variables
    32. 31.32. Int32 or Nil
    33. 31.33. Resources
62. 32. Crystal from 0 to Web site
63. 1. 32.1. Crystal from 0 to Web site
    2. 32.2. Background
    3. 32.3. Why?
    4. 32.4. I can do better
    5. 32.5. How to learn
    6. 32.6. When
    7. 32.7. Shardbox
    8. 32.8. What did I learn?
    9. 32.9. Crystal is fun
    10. 32.10. Shards
    11. 32.11. Code formatter
    12. 32.12. Ameba - Linter
    13. 32.13. Spectator - testing framework
    14. 32.14. Code coverage
    15. 32.15. CI - GitHub Actions
    16. 32.16. The language
    17. 32.17. What do ? and ! mean?!
    18. 32.18. Emojis and Unicode characters 💎
    19. 32.19. Meaning of ?
    20. 32.20. Meaning of !
    21. 32.21. Web framework?
    22. 32.22. Amber Framework
    23. 32.23. Lucky Framework
    24. 32.24. Kemal
    25. 32.25. Crinja
    26. 32.26. Shardbox
    27. 32.27. Future
    28. 32.28. Thank you - QA ?!?!
64. 33. Macros
65. 1. 33.1. Macro - increment x by 1
    2. 33.2. Macro - with parameter and placeholder
    3. 33.3. Macro Swap
    4. 33.4. Macro - internal variables - Swap fixed
    5. 33.5. Macros function
    6. 33.6. Macro to print type and content