Don't use a default argument. Use *args
to collect all the arguments into an array.
def my_count(*args, &block)
if args.length == 1 && !block_given?
# use args[0]
elsif args.length == 1 && block_given?
# use block
elsif args.length == 0 && !block_given?
# no argument/block
else
# raise error
end
end