From: Robert Klemme <shortcutter@...>
Date: 2007-08-07T17:59:29+09:00
Subject: Re: Feature request (pretty_inspect variant, yielding single quotes instead of double)

2007/8/7, Ronald Fischer <ronald.fischer@venyon.com>:
> 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?

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