# Feature request (pretty\_inspect variant, yielding single quo **URL:** \ **Category:** Ruby\ **Created:** [August 7, 2007, 10:42am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435 "2007-08-07T10:42:17Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 10:42am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/1 "2007-08-07T10:42:17Z")
require ‘pp’ s=‘abc’ t=‘#{a}’ print s.pretty\_inspect print t.pretty\_inspect this outputs: “abc” “#{a}” This is of course correct - both show the content of the strings, and both print it in a way that this can be used in an eval to get the original string back: eval(‘t1=’+t.pretty\_inspect.chomp) # ==\> t1==t My main objection is that from a viewpoint of readability, it would be better if pretty\_inspect would generate single quoted strings instead of double quoted ones, since less -escaping is necessary in this case. Since changing the present implementation of pretty\_inspect might break existing code, I suggest that - either pretty\_inspect takes an additional argument which tells what type of string quotation shall be used for producing the output string in the case of pretty-printing strings, or - provide an additional function in pp (say: pretty\_inspectq), which formats strings by using single quotes. The first variant would be more flexible (as we could then even require ‘abc’.pretty\_inspect(‘%q()’), producing %q(abc) in return), but causes more work. For the second variant, the current code of pretty\_inspect can be reused, changing just the part which formats strings. Here is an implementation suggestion for pretty\_inspectq-ing a string s: “'”+s.gsub(/([^\]|^)‘/,’\1\\‘+"’“)+”'" Any opinions on this? ## Ronald Ronald F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Phone: +49-89-452133-162 ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:00am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/2 "2007-08-07T11:00:20Z")
2007/8/7, Ronald F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > This is of course correct - both show the content of the strings, > Since changing the present implementation of pretty\_inspect might > even require ‘abc’.pretty\_inspect(‘%q()’), producing %q(abc) > in return), but causes more work. For the second variant, > the current code of pretty\_inspect can be reused, changing > just the part which formats strings. Here is an implementation > suggestion for pretty\_inspectq-ing a string s: > > “'”+s.gsub(/([^\]|^)‘/,’\1\\‘+"’“)+”'" > > Any opinions on this? You would have to also explain how embedded control characters will be printed because there is no way I know of at the moment that would allow to embed e.g. a newline in a single quote string: irb(main):006:0\> “\n” =\> “\n” irb(main):007:0\> ‘\n’ =\> “\n” irb(main):009:0\> “\064” =\> “4” irb(main):010:0\> ‘\064’ =\> “\064” If you introduce a new syntax then the output of pp becomes inconsistent with what Ruby normally understands to be single quoted strings. I believe you would have to have better reasons than readability to introduce this inconsistency and make pp’s output less useful in terms of reuse (copy and paste). Personally I doubt it is worthwhile. Btw, there is another variant for switching between single and double quotes: you can use a global variable. This has the advantage that you do not need to touch any #inspect implementation of custom classes - but comes at a price of course. Kind regards robert ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:10am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/3 "2007-08-07T11:10:23Z")
> You would have to also explain how embedded control characters will be > printed because there is no way I know of at the moment that would > allow to embed e.g. a newline in a single quote string: Good point. I overlooked this. But there are easy workarounds. For example, pretty\_inspectq could revert to double quotation if the string to be printed can not be formatted using single quotes. Or (remember that I don’t want to change the default behaviour of pretty\_inspect) an exception is thrown in this case, which makes sense: The user requests pretty\_inspecting in single quotes, but if it is not possible, we should blame the user. > If you introduce a new syntax Certainly not! I don’t want to open _that_ can of worms. > Btw, there is another variant for switching between single and double > quotes: you can use a global variable. This has the advantage that > you do not need to touch any #inspect implementation of custom classes > > - but comes at a price of course. Hmmmmm… here I don’t see the point. In my case, I use pretty\_inspect to “marshal” Ruby data types (they are written to a file, which is then edited by the user, and finally eval’ed by another Ruby application). I use pretty\_inspect to easily format Ruby structures (arrays…), but for the user, it is more convenient to use single quoted strings when editing the data, because he needs to care less about escaping rules. Ronald ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:27am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/4 "2007-08-07T11:27:28Z")
2007/8/7, Ronald F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > thrown in > > > you do not need to touch any #inspect implementation of custom classes > > > > - but comes at a price of course. > > Hmmmmm… here I don’t see the point. Global variables are generally considered bad OO and you should normally try to avoid them if possible. > In my case, I use pretty\_inspect to “marshal” Ruby data types (they > are written to a file, which is then edited by the user, and finally > eval’ed by another Ruby application). I use pretty\_inspect to easily > format Ruby structures (arrays…), but for the user, it is more > convenient > to use single quoted strings when editing the data, because he needs > to care less about escaping rules. The proper way to do this would of course be a decent parser because eval has serious security implications. 🙂 You could use YAML or XML for this although I believe you will find XML too verbose. 🙂 Kind regards robert ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:18am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/5 "2007-08-07T11:18:24Z")
Here’s what I suggest: class String def quote(str="’") “#{str}#{self}#{str}” end def quote!(str="’") self.insert(0, str) \<\< str end end #Tests test = “abc” =\> “abc” test.quote =\> “‘abc’” test.quote(""") =\> ““abc”” test.quote(“123”) =\> “123abc123” test =\> “abc” test.quote! =\> “‘abc’” test =\> “‘abc’” ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:59am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/6 "2007-08-07T11:59:32Z")
2007/8/7, Ronald F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > > Global variables are generally considered bad OO and you should > > normally try to avoid them if possible. > > You got me wrong here: I wanted to say that I don’t see how globals > would help me here. The global would be the flag which quoting style to use. Advantage is that you do not need to pass it around (i.e. if YourClass#inspect has some String members whose #inspect output it includes in its own output). > Yes, security implications for instance. The user could arbitrarily ruin > anything by inserting suitable statements. Only that in _this_ case, > security is a non-issue, but time to invest in the implementation is > one. If I define the file format as “Ruby code”, parsing is trivial, > as it is done by Ruby; and creating the file is also trivial, using > pretty\_inspect. Just wanted to make sure you are aware of the implications. If it’s not an issue, good. Cheers robert ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 12:53pm UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/7 "2007-08-07T12:53:35Z")
> > You got me wrong here: I wanted to say that I don’t see how globals > > would help me here. > > The global would be the flag which quoting style to use. Advantage is > that you do not need to pass it around (i.e. if YourClass#inspect has > some String members whose #inspect output it includes in its own > output). Ah, I see. No, this would definitely be a terrible hack which we should avoid! After all this feedback, I think the best solution would be to start with one of my originally proposed solutions (either a new function, or having pretty\_inspect accepting a parameter), and either throwing an exception or returning nil if the conversion can’t be done. Ronald ---
**Author:** ![ronaldfischer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/67e7ee/32.png) [@ronaldfischer](https://www.ruby-forum.com/u/ronaldfischer)\ **Post date:** [August 7, 2007, 11:35am UTC](https://www.ruby-forum.com/t/feature-request-pretty-inspect-variant-yielding-single-quo/111435/8 "2007-08-07T11:35:28Z")
> Global variables are generally considered bad OO and you should > normally try to avoid them if possible. You got me wrong here: I wanted to say that I don’t see how globals would help me here. > > In my case, I use pretty\_inspect to “marshal” Ruby data types (they > > are written to a file, which is then edited by the user, and finally > > eval’ed by another Ruby application). I use pretty\_inspect to easily > > format Ruby structures (arrays…), but for the user, it is more > > convenient > > to use single quoted strings when editing the data, because he needs > > to care less about escaping rules. > > The proper way to do this would of course be a decent parser because > eval has serious security implications. Yes, security implications for instance. The user could arbitrarily ruin anything by inserting suitable statements. Only that in _this_ case, security is a non-issue, but time to invest in the implementation is one. If I define the file format as “Ruby code”, parsing is trivial, as it is done by Ruby; and creating the file is also trivial, using pretty\_inspect. Ronald