1 files changed, 62 insertions, 0 deletions
diff --git a/examples/getoptlong/fibonacci.rb b/examples/getoptlong/fibonacci.rb
new file mode 100644
index 0000000000..24a2aab3c3
--- /dev/null
+++ b/examples/getoptlong/fibonacci.rb
@@ -0,0 +1,62 @@
+require 'getoptlong'
+
+options = GetoptLong.new(
+  ['--number', '-n', GetoptLong::REQUIRED_ARGUMENT],
+  ['--verbose', '-v', GetoptLong::OPTIONAL_ARGUMENT],
+  ['--help', '-h', GetoptLong::NO_ARGUMENT]
+)
+
+def help(status = 0)
+  puts <<~HELP
+    Usage:
+
+      -n n, --number n:
+        Compute Fibonacci number for n.
+      -v [boolean], --verbose [boolean]:
+        Show intermediate results; default is 'false'.
+      -h, --help:
+        Show this help.
+  HELP
+  exit(status)
+end
+
+def print_fibonacci (number)
+  return 0 if number == 0
+  return 1 if number == 1 or number == 2
+  i = 0
+  j = 1
+  (2..number).each do
+    k = i + j
+    i = j
+    j = k
+    puts j if @verbose
+  end
+  puts j unless @verbose
+end
+
+options.each do |option, argument|
+  case option
+  when '--number'
+    @number = argument.to_i
+  when '--verbose'
+    @verbose = if argument.empty?
+      true
+    elsif argument.match(/true/i)
+      true
+    elsif argument.match(/false/i)
+      false
+    else
+      puts '--verbose argument must be true or false'
+      help(255)
+    end
+  when '--help'
+    help
+  end
+end
+
+unless @number
+  puts 'Option --number is required.'
+  help(255)
+end
+
+print_fibonacci(@number)