runtime/pattern_matching_parens.rb

tests/_examples/runtime/pattern_matching_parens.rb in the metorex repository.

# Pattern matching with `case` and `in`: literals, bindings, array and hash
# patterns, rest patterns, guards and nesting.

# Example 1: Literal pattern matching
value = 42
case value
in 0
  puts("Zero")
in 42
  puts("The answer!")
in _
  puts("Something else")
end

# Example 2: Identifier pattern (variable binding)
case 100
in x
  puts("Matched: #{x}")
end

# Example 3: Array destructuring
arr = [1, 2, 3]
case arr
in [a, b, c]
  puts("a=#{a}, b=#{b}, c=#{c}")
end

# Example 4: Array with rest pattern
numbers = [1, 2, 3, 4, 5]
case numbers
in [first, *rest]
  puts("First: #{first}")
  puts("Rest: #{rest}")
end

# Example 5: Rest in the middle
case numbers
in [first, *middle, last]
  puts("First: #{first}, Last: #{last}")
  puts("Middle: #{middle}")
end

# Example 6: Object/Dictionary destructuring
point = {x: 10, y: 20}
case point
in {x:, y:}
  puts("Point at (#{x}, #{y})")
end

# Example 7: Guard clause
temperature = 75
case temperature
in t if t > 80
  puts("Hot!")
in t if t > 60
  puts("Warm")
in t if t > 40
  puts("Cool")
in _
  puts("Cold!")
end

# Example 8: Nested patterns
data = [[1, 2], [3, 4]]
case data
in [[a, b], [c, d]]
  sum = a + b + c + d
  puts("Sum: #{sum}")
end

# Example 9: Mixed types in array
mixed = [1, "hello", true]
case mixed
in [num, str, bool]
  puts("Number: #{num}")
  puts("String: #{str}")
  puts("Boolean: #{bool}")
end

# Example 10: Multiple cases with specific patterns
status = 404
case status
in 200
  puts("OK")
in 404
  puts("Not Found")
in 500
  puts("Internal Server Error")
in code
  puts("Status code: #{code}")
end

# Example 11: String pattern matching
command = "start"
case command
in "start"
  puts("Starting...")
in "stop"
  puts("Stopping...")
in "restart"
  puts("Restarting...")
in _
  puts("Unknown command")
end

# Example 12: Boolean pattern matching
flag = true
case flag
in true
  puts("Flag is true")
in false
  puts("Flag is false")
end

# Example 13: Nil pattern matching
maybe_value = nil
case maybe_value
in nil
  puts("No value")
in x
  puts("Value: #{x}")
end

# Example 14: Complex guard with multiple conditions
age = 25
case age
in a if a >= 18 and a < 65
  puts("Working age")
in a if a < 18
  puts("Minor")
in _
  puts("Retirement age")
end

# Example 15: Wildcard in array patterns
data = [1, 2, 3, 4]
case data
in [1, _, _, last]
  puts("First is 1, last is #{last}")
end

Output:

The answer!
Matched: 100
a=1, b=2, c=3
First: 1
Rest: [2, 3, 4, 5]
First: 1, Last: 5
Middle: [2, 3, 4]
Point at (10, 20)
Warm
Sum: 10
Number: 1
String: hello
Boolean: true
Not Found
Starting...
Flag is true
No value
Working age
First is 1, last is 4