# Bug in Ruby with adding strings? **URL:** \ **Category:** Ruby\ **Created:** [January 19, 2007, 10:56pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717 "2007-01-19T22:56:13Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 19, 2007, 10:56pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/1 "2007-01-19T22:56:13Z")
## I just found what looks like a bug in Ruby 184-20. (I haven’t tried it in newer builds.) Here’s a simple script that will expose this bug: ## irb(main):001:0\> x = 1 =\> 1 irb(main):002:0\> puts ‘foo’ + x.to\_s +‘bar’ SyntaxError: compile error (irb):2: syntax error puts ‘foo’ + x.to\_s +‘bar’ ^ from (irb):2 I finally figured out that it was the Plus sign _right next_ to the “bar”, _after_ the “to\_s” method that Ruby dislikes. If I insert a space, I get the correct output. If I take out both spaces, I get the correct output. It’s only if there’s a space after the “to\_s” and none between the Plus sign and string-in-quotes that it blows up. That is: > puts ‘foo’ + x.to\_s + ‘bar’ # this works > puts ‘foo’ + x.to\_s +‘bar’ # doesn’t work > puts ‘foo’ + x.to\_s+ ‘bar’ # this works > puts ‘foo’ + x.to\_s+‘bar’ # this works Anyone know why this might be? I haven’t played with it anymore, so I wonder if this bug exists with other methods. Paul ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 19, 2007, 11:11pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/2 "2007-01-19T23:11:15Z")
I suspect that having no space after the + makes Ruby think it is a unary operator. And since to\_s is a method, Ruby thinks that you’re passing +‘bar’ to x.to\_s. This can’t be the only problem, though, since it is giving you a SyntaxError before it actually complains about passing an unexpected argument to to\_s… ``` David ``` ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 20, 2007, 9:56am UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/3 "2007-01-20T09:56:07Z")
On 19.01.2007 23:07, removed\_email\_address@domain.invalid wrote: > I suspect that having no space after the + makes Ruby think it is a > unary operator. And since to\_s is a method, Ruby thinks that you’re > passing +‘bar’ to x.to\_s. This can’t be the only problem, though, > since it is giving you a SyntaxError before it actually complains about > passing an unexpected argument to to\_s… I think it’s trying to parse as puts(‘foo’ + x.to\_s, +‘bar’) where the comma is missing. So it thinks +‘bar’ is not an argument to to\_s but to puts. Regards robert ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 20, 2007, 8:11pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/4 "2007-01-20T20:11:13Z")
Robert K. wrote: > I think it’s trying to parse as > puts(‘foo’ + x.to\_s, +‘bar’) > > where the comma is missing. So it thinks +‘bar’ is not an argument to > to\_s but to puts. I originally came across this when I was trying to assign something similar to a variable (trying to create a filename). That is: filename = ‘foo’ + x.to\_s +‘bar’ Would it still be trying to use the +‘bar’ as an argument when trying to do an assignment? ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 22, 2007, 8:16pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/5 "2007-01-22T20:16:26Z")
Thanks for the feedback Robert. I didn’t know Ruby could do that. I’ll just try to be more consistent with spaces and plus signs to avoid this problem again. Cheers. Paul. =) ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 22, 2007, 8:24pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/6 "2007-01-22T20:24:29Z")
On 1/20/07, Paul [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > similar to a variable (trying to create a filename). > > That is: filename = ‘foo’ + x.to\_s +‘bar’ > > Would it still be trying to use the +‘bar’ as an argument when trying > to do an assignment? it may be parsing as ‘foo’ + x.to\_s(+‘bar’) since to\_s can sometimes take an argument. ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 21, 2007, 11:55am UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/7 "2007-01-21T11:55:42Z")
On 20.01.2007 20:07, Paul wrote: > That is: filename = ‘foo’ + x.to\_s +‘bar’ > > Would it still be trying to use the +‘bar’ as an argument when trying > to do an assignment? Dunno. Maybe. This is valid Ruby: irb(main):001:0\> a = 1,2,3 =\> [1, 2, 3] So you _can_ have multiple values on the right (as well as on the left). Kind regards robert ---
**Author:** ![paul](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/bbe5ce/32.png) [@paul](https://www.ruby-forum.com/u/paul)\ **Post date:** [January 22, 2007, 9:00pm UTC](https://www.ruby-forum.com/t/bug-in-ruby-with-adding-strings/82717/8 "2007-01-22T21:00:35Z")
Gregory B. schrieb: > it may be parsing as ‘foo’ + x.to\_s(+‘bar’) since to\_s can sometimes > take an argument. This makes sense. When translating the infix notation to method usage (don’t know if this will be done by the interpreter), the first step is ‘foo’ + x.to\_s +‘bar’ =\> ‘foo’.+(x.to\_s +‘bar’) “String#+” has one argument, so “x.to\_s +‘bar’” must be one argument. When looking to “x” it is not clear for the interpreter, what the result of “x.to\_s” will be, but it knows, that “to\_s” has an (optional) argument. So it tries to find “String#+@” method for ‘bar’ and fails. The possibility to backtrack after failure and try first to evaluate “x.to\_s”, which returns the string “‘1’”, an then to compute “‘1’ +‘bar’” (works without any problem) will not be done due to good reasons for the general case. Wolfgang Nádasi-Donner