# Ambiguous first argument? **URL:** \ **Category:** ruby-talk\ **Created:** [19 August 2010 00:39 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689 "2010-08-19T00:39:13Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Roger\_Pack4](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@Roger\_Pack4](https://rubytalk.org/u/Roger_Pack4)\ **Post date:** [19 August 2010 00:39 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689/1 "2010-08-19T00:39:13Z")
Hi all. With this code: memory\_bitmap.scan /\x00{5}+/ I get this warning: test.rb:1: warning: ambiguous first argument; put parentheses or even spaces Could somebody please help me to understand what exactly is ambiguous there? Thank you! -r > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Ryan\_Davis1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/ryan_davis1/32/1848_2.png) [@Ryan\_Davis1](https://rubytalk.org/u/Ryan_Davis1)\ **Post date:** [19 August 2010 01:51 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689/2 "2010-08-19T01:51:09Z")
2 / 2 2 / 2 / > **···** > > On Aug 18, 2010, at 17:39 , Roger Pack wrote: > > > Hi all. > > With this code: > > > > memory\_bitmap.scan /\x00{5}+/ > > > > I get this warning: > > > > test.rb:1: warning: ambiguous first argument; put parentheses or even > > spaces > > > > Could somebody please help me to understand what exactly is ambiguous > > there? ---
**Author:** ![GianFranco\_Bozzetti](https://avatars.discourse-cdn.com/v4/letter/g/7c8e57/32.png) [@GianFranco\_Bozzetti](https://rubytalk.org/u/GianFranco_Bozzetti)\ **Post date:** [19 August 2010 15:26 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689/3 "2010-08-19T15:26:54Z")
Roger Pack wrote: > Hi all. > With this code: > > memory\_bitmap.scan /\x00{5}+/ > > I get this warning: > > test.rb:1: warning: ambiguous first argument; put parentheses or even > spaces > > Could somebody please help me to understand what exactly is ambiguous > there? > Thank you! > -r The ambiguity comes from the double quantifier {5}+ where: - {5} means exactly 5 occurrences of \x00 - + means 1 or more occurrences of preceding expression. Given the string: bitmap="\x30\x50\-\x00\x00\x00\x00\x00\x00\-\x40\x50\x30" p bitmap.scan(/\x00+/) #=\> ["\000\000\000\000\000\000"] p bitmap.scan(/\x00{2}/) #=\> ["\000\000", "\000\000", "\000\000"] HTH gfb > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Rob\_Biedenharn1](https://avatars.discourse-cdn.com/v4/letter/r/57b2e6/32.png) [@Rob\_Biedenharn1](https://rubytalk.org/u/Rob_Biedenharn1)\ **Post date:** [19 August 2010 15:42 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689/4 "2010-08-19T15:42:53Z")
I think the ambiguity is actually in parsing: memory\_bitmap.scan / \x00 { 5 } + / Is that perhaps dividing by the result of calling \x00 with a block? Spaces won't help in this case, but some nice parentheses will do. memory\_bitmap.scan(/\x00{5}+/) That will ensure that the parser sees /\x00{5}+/ as an argument to the scan method. Whether the Regexp does what you want/expect is another question. -Rob Rob Biedenharn Rob@AgileConsultingLLC.com [http://AgileConsultingLLC.com/](http://AgileConsultingLLC.com/) rab@GaslightSoftware.com [http://GaslightSoftware.com/](http://GaslightSoftware.com/) > **···** > > On Aug 19, 2010, at 11:26 AM, Gianfranco Bozzetti wrote: > > > Roger Pack wrote: > > > > > Hi all. > > > With this code: > > > > > > memory\_bitmap.scan /\x00{5}+/ > > > > > > I get this warning: > > > > > > test.rb:1: warning: ambiguous first argument; put parentheses or even > > > spaces > > > > > > Could somebody please help me to understand what exactly is ambiguous > > > there? > > > Thank you! > > > -r > > > > The ambiguity comes from the double quantifier {5}+ where: > > - {5} means exactly 5 occurrences of \x00 > > - + means 1 or more occurrences of preceding expression. > > > > Given the string: > > bitmap="\x30\x50\-\x00\x00\x00\x00\x00\x00\-\x40\x50\x30" > > > > p bitmap.scan(/\x00+/) #=\> ["\000\000\000\000\000\000"] > > p bitmap.scan(/\x00{2}/) #=\> ["\000\000", "\000\000", "\000\000"] > > > > HTH gfb > > -- Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Roger\_Pack4](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@Roger\_Pack4](https://rubytalk.org/u/Roger_Pack4)\ **Post date:** [19 August 2010 15:50 UTC](https://rubytalk.org/t/ambiguous-first-argument/59689/5 "2010-08-19T15:50:22Z")
> I think the ambiguity is actually in parsing: > > memory\_bitmap.scan / \x00 { 5 } + / > Is that perhaps dividing by the result of calling \x00 with a block? Interesting. Ok thanks for all the responses. It does work as expected 🙂 -r > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).