Learn CRYSTAL with Real Code Examples

count = 0
is_dark = false

def update_ui(count, is_dark)
    puts "Counter: #{count}"
    puts "Theme: #{is_dark ? "Dark" : "Light"}"
end

def increment(count, is_dark)
    count += 1
    update_ui(count, is_dark)
    count
end

def decrement(count, is_dark)
    count -= 1
    update_ui(count, is_dark)
    count
end

def reset(count, is_dark)
    count = 0
    update_ui(count, is_dark)
    count
end

def toggle_theme(is_dark)
    is_dark = !is_dark
    update_ui(count, is_dark)
    is_dark
end

# Simulate actions
update_ui(count, is_dark)
count = increment(count, is_dark)
count = increment(count, is_dark)
is_dark = toggle_theme(is_dark)
count = decrement(count, is_dark)
count = reset(count, is_dark)

Demonstrates a simple counter with theme toggling using Crystal variables and console output.

def add(a, b)
    a + b
end

puts add(10, 20)

Adds two numbers and prints the result.

def factorial(n)
    return 1 if n <= 1
    n * factorial(n - 1)
end

puts factorial(5)

Calculates factorial recursively.

def fib(n)
    return n if n < 2
    fib(n - 1) + fib(n - 2)
end

10.times do |i|
    puts fib(i)
end

Generates first 10 Fibonacci numbers.

def max(a, b)
    a > b ? a : b
end

puts max(10, 20)

Finds the maximum of two numbers.

arr = [1,2,3,4,5]
puts arr.sum

Sums elements of an array.

arr = [1,2,3,4,5]
arr.each do |x|
    puts x if x.even?
end

Prints even numbers from an array.

count = 3
count += 1 if count < 5
puts count

Increment counter only if less than 5.

count = 0
count += 1
count += 1
puts count
count = 0
puts count

Counter that increments and can be reset.

is_dark = false
puts is_dark ? "Dark" : "Light"
is_dark = !is_dark
puts is_dark ? "Dark" : "Light"
is_dark = !is_dark
puts is_dark ? "Dark" : "Light"

Toggles theme multiple times.