#
# extract_digits
# --------------
# Walks through the input string and collects only characters
# that are recognized as digits. Ruby's regular expressions
# provide a concise and efficient way to filter characters.
#
# Using `scan(/\d/)` returns an array of all digit matches,
# and `join` builds the final string.
#
def extract_digits(str)
# Scan for digit characters and join them into a single string
str.scan(/\d/).join
end
#
# Main execution
#
str = '5 ruby8go 9001 c c++ 17python'
# Extract digits
digits = extract_digits(str)
# Display results
puts "Original: #{str}"
puts "Digits: #{digits}"
#
# run:
#
# Original: 5 ruby8go 9001 c c++ 17python
# Digits: 58900117
#
