# Puts returns nil? **URL:** \ **Category:** Ruby\ **Created:** [January 5, 2007, 10:30am UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160 "2007-01-05T10:30:19Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 5, 2007, 10:30am UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/1 "2007-01-05T10:30:19Z")
Hi, I’m sorry to be asking such a daft question but I need a concept explaining… I’m working through the excellent Chris P. book ‘Learn to program’ and I don’t get one of the examples he gives. In particular I don’t follow the following example: def say\_moo number\_of\_moos puts ‘mooooooo…’ \* number\_of\_moos ‘yellow submarine’ end x = say\_moo 3 puts x.capitalize + ‘, dude…’ puts x + ‘.’ Now the output from this is: mooooooo…mooooooo…mooooooo Yellow submarine, dude… yellow submarine * * * OK, so here’s the problem, I _don’t_ get why it doesn’t return the following: mooooooo…mooooooo…mooooooo Yellow submarine, dude… mooooooo…mooooooo…mooooooo yellow submarine * * * Why do we get one set of ‘moos’ but not a second? Sorry for such a newbiee question. Cheers arfon ---
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 5, 2007, 10:53am UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/2 "2007-01-05T10:53:06Z")
Arfon S. wrote: > Hi, I’m sorry to be asking such a daft question but I need a concept > explaining… > > I’m working through the excellent Chris P. book ‘Learn to program’ and > I don’t get one of the examples he gives. In particular I don’t follow > the following example: > > def say\_moo number\_of\_moos > puts ‘mooooooo…’ \* number\_of\_moos > ‘yellow submarine’ > end > > x = say\_moo 3 > puts x.capitalize + ‘, dude…’ > puts x + ‘.’ > > Now the output from this is: > > mooooooo…mooooooo…mooooooo > Yellow submarine, dude… > yellow submarine > > * * * > > OK, so here’s the problem, I _don’t_ get why it doesn’t return the > following: > > mooooooo…mooooooo…mooooooo > Yellow submarine, dude… > mooooooo…mooooooo…mooooooo > yellow submarine > > * * * > > Why do we get one set of ‘moos’ but not a second? > > Sorry for such a newbiee question. > > Cheers > > arfon Hi Arfon in every ruby-function, the last statement (here ‘yellow submarine’) is the return-value of this function, nothing else ! Further yes, puts returns nil. puts(obj, …) =\> nil You can see the declaration of all ruby-functions in the “fxri”, installed with your ruby-interpreter. It’s very helpful to work with it. 3. If you intention was to append the ‘yellow submarine’ to the puts 1 line above, you need an ‘+’ to do this: puts ‘mooooooo…’ \* 3 + ‘yellow submarine’ mooooooo…mooooooo…mooooooo…yellow submarine best regards Jörg ---
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 5, 2007, 11:05am UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/3 "2007-01-05T11:05:26Z")
Jörg Abelshauser wrote: > Arfon S. wrote: > > > Hi, I’m sorry to be asking such a daft question but I need a concept > > explaining… > > > > I’m working through the excellent Chris P. book ‘Learn to program’ and > > I don’t get one of the examples he gives. In particular I don’t follow > > the following example: > > > > def say\_moo number\_of\_moos > > puts ‘mooooooo…’ \* number\_of\_moos > > ‘yellow submarine’ > > end > > > > x = say\_moo 3 > > puts x.capitalize + ‘, dude…’ > > puts x + ‘.’ > > > > Now the output from this is: > > > > mooooooo…mooooooo…mooooooo > > Yellow submarine, dude… > > yellow submarine > > > > * * * > > > > OK, so here’s the problem, I _don’t_ get why it doesn’t return the > > following: > > > > mooooooo…mooooooo…mooooooo > > Yellow submarine, dude… > > mooooooo…mooooooo…mooooooo > > yellow submarine > > > > * * * > > > > Why do we get one set of ‘moos’ but not a second? > > > > Sorry for such a newbiee question. > > > > Cheers > > > > arfon > > Hi Arfon > in every ruby-function, the last statement (here ‘yellow submarine’) is > the return-value of this function, nothing else ! > Further yes, puts returns nil. > puts(obj, …) =\> nil > You can see the declaration of all ruby-functions in the “fxri”, > installed with your ruby-interpreter. It’s very helpful to work with it. > 3. If you intention was to append the ‘yellow submarine’ to the puts 1 > line above, you need an ‘+’ to do this: > > puts ‘mooooooo…’ \* 3 + ‘yellow submarine’ > mooooooo…mooooooo…mooooooo…yellow submarine > > best regards Jörg Ahh, OK, thanks for this. I think I was confused as I thought the first ‘puts’, i.e. puts x.capitalize + ‘, dude…’ was producing the moos and the second one (puts x + ‘.’) wasn’t. Both of the puts are just returning the last statement, it’s the ‘x= say\_moo 3’ that is giving the moooo…mooooo…moooooo… Right?! Cheers arfon ---
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 6, 2007, 7:30pm UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/4 "2007-01-06T19:30:42Z")
Arfon S. wrote: > […] A method returns the value of the last statement, not a list of all of them. In your method, the return value of puts (which is nil, btw) is discarded. > def say\_moo number\_of\_moos > puts ‘mooooooo…’ \* number\_of\_moos > ‘yellow submarine’ > end > > x = say\_moo 3 Here you call say\_moo. Say\_moo puts 3 moo’s in you screen, then returns ‘yellow submarine’. This return value is assigned to x. > puts x.capitalize + ‘, dude…’ Puts the value of x (‘yellow submarine’) capitalized, plus ‘, dude…’. > puts x + ‘.’ Puts the value of x, plus a dot. HTH. Good luck. ---
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 6, 2007, 7:30pm UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/5 "2007-01-06T19:30:52Z")
Alle 10:30, venerdì 5 gennaio 2007, Arfon S. ha scritto: > puts ‘mooooooo…’ \* number\_of\_moos > Yellow submarine, dude… > mooooooo…mooooooo…mooooooo > arfon > say\_moo does two separate things: > 1- writes the string ‘mooooooo…’ on the screen number\_of\_moos times > 2- returns the string ‘yellow submarine’ > The call to puts in the definition of say\_moo has nothing to do with > say\_moo’s > return value, which is determinated by the method’s last line: ‘yellow > submarine’. Writing x=say\_moo 3 will put in x only the string ‘yellow submarine’, because this is what say\_moo returns. In other words, the line mooooooo…mooooooo…mooooooo is written by a side effect of say\_moo; the other two lines are produced by your own puts statements. To get the output you expected (well, not exactly, captialize would work a little differently), say\_moo should have defined like this: def say\_moo number\_of\_moos mooooooo…’ \* number\_of\_moos+"\nyellow submarine" end In this case, say\_moo wouldn’t write nothing on the screen by itself, but would return the string “mooooooo…mooooooo…mooooooo yellow submarine” which would be written twice by your puts statements I hope this helps Stefano ---
**Author:** ![arfon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/f4b2a3/32.png) [@arfon](https://www.ruby-forum.com/u/arfon)\ **Post date:** [January 6, 2007, 7:30pm UTC](https://www.ruby-forum.com/t/puts-returns-nil/81160/6 "2007-01-06T19:30:35Z")
because you only call say\_moo once. x = say\_moo 3 the interpreter will resolve and execute the method call and will store the _result_ in x thus say\_moo is called once and x is set to the string “Yellow submarine” puts x this will only print the content of x which is a string and won’t call say\_moo another time did it help ? jean