Newbie question

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March 4th, 2012, 06:00 AM

ArXi

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Newbie question

hello everyone,
here i have this little script:

Code:

def compare
puts "Enter a word or a phrase: "
val = gets.chomp!
val1=val.downcase.reverse.gsub(/\W/,"")
if val1 == val1.reverse
print "Its a palindrome :)"
else print "Its not a palindrome "
end
compare
end

i wondering how i can make it run only once ? i want it to work like i give a word, script checks it, gives me an answer and stops. because now after all this it asks me to give another word again and again.

July 24th, 2012, 03:01 AM

leo.jnag

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Quote:

Originally Posted by ArXi

hello everyone,
here i have this little script:

Code:

def compare
puts "Enter a word or a phrase: "
val = gets.chomp!
val1=val.downcase.reverse.gsub(/\W/,"")
if val1 == val1.reverse
print "Its a palindrome :)"
else print "Its not a palindrome "
end
compare
end

Your code is recursive. so you should remove compare from the def. the code will be

Code:

def compare
puts "Enter a word or a phrase: "
val = gets.chomp!
val1=val.downcase.reverse.gsub(/\W/,"")
if val1 == val1.reverse
print "Its a palindrome :)"
else print "Its not a palindrome "
end
end

compare

July 24th, 2012, 08:54 PM

Jacques1

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Hi,

This recursion is wrong, anyway. Since the methods never return, the call stack just keeps growing until it's eventually full (raising a SystemStackError).

You'd have to use an endless loop for that (or advanced features like Fibers).

July 26th, 2012, 03:51 AM

leo.jnag

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Quote:

Originally Posted by Jacques1

ArXi doesn't want repetition of input requests from the program.
He doesn't want recursion.

July 26th, 2012, 06:41 AM

Jacques1

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Yes, I did read that, and you already answered his question, didn't you?

My point is that he mustn't ever use this looping approach. So even when one day he actually wants to do an endless loop (not this time), he mustn't use recursion.

I hope that clears it up.

July 30th, 2012, 05:23 AM

bdeveloper01

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def compare
puts "Enter a word or a phrase: "
val = gets.chomp!
val.length
if(val.length == 0)
puts "-----------------------"
puts "Your input is not Valid"
puts "-----------------------"
return compare()
end
val1=val.downcase.reverse.gsub(/\W/,"")
if val1 == val1.reverse
print "Its a palindrome

"
else
print "Its not a palindrome "
end
end

compare()

By
bdeveloper01

July 30th, 2012, 06:27 AM

Jacques1

pollyanna

Join Date: Jul 2012

Location: Germany

Posts: 2,014

Time spent in forums: 1 Month 2 Weeks 6 Days 11 h 26 m 31 sec
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Well, that's the exact same error we were talking about.

Do not use recursion for potentially endless loops (unless the language supports it and you know what you're doing). Sure, a user probably won't hit Enter 1000 times. But it's still very bad style, because if he actually does, the call stack will blow up.

Use a while loop or exception handling:

Code:

puts 'Enter a word or a phrase:'
input = gets.chomp
while input.empty?
  puts 'Your input is not valid'
  input = gets.chomp
end

Code:

InputError = Class.new StandardError

puts 'Enter a word or a phrase:'
begin
  input = gets.chomp
  raise InputError, 'Your input is not valid' if input.empty?
rescue InputError => error
  puts error.message
  retry
end

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