Problem with stripping leading whitespace in here documents

Discussion in 'Ruby' started by Douglas Wells, Jan 25, 2007.

  1. I'm writing a number of test cases. I would like the input data to
    behave like a file, and I would like to include that data within
    the test file (in order to reduce the proliferation of files and
    eliminate the necessity of tracking an additional, separate file
    for each test case). Similar mechanisms would include BASIC's
    DATA statements, or Perl's DATA filehandle. I don't know of an
    analogue in ruby. Any suggestions?

    Instead I am using Bourne shell-type here-documents. But, I am
    encountering a problem. The Bourne shell supports the concept of
    stripping leading white space, and Ruby seems to support the same
    notion (from .../doc/ruby18/ruby-man/syntax.html):

    "If the - [is] placed before the delimiter, then all leading
    whitespcae [sic] characters (tabs or spaces) are stripped from
    input lines and the line containing [the] delimiter. This
    allows here-documents within scripts to be indented in a natural
    fashion."

    which is the same syntax as the Bourne shell.

    But, if I run the following script:

    # Start of script:
    input1 = <<EOF
    abc
    def
    EOF

    input2 = <<-EOF
    ghi
    jkl
    EOF

    p input1
    p input2
    # End of script.

    I get the following output:

    "abc\ndef\n"
    "\tghi\n\tjkl\n"

    Note that the leading tab has NOT been removed in the here-document
    that should be stripped (input2). (It is a tab in the original file.)

    Is this a bug? or am I missing something in the documentation.
    I'm using 'ruby 1.8.5 (2006-12-25 patchlevel 12) [i386-freebsd6]'.

    (And yes, I know how to strip the leading whitespace with a function
    after reading it. I'm particularly addressing the issue with here
    documents.)

    Thanks, - dmw
     
    Douglas Wells, Jan 25, 2007
    #1
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  2. Douglas Wells

    Brad Ediger Guest

     
    Brad Ediger, Jan 25, 2007
    #2
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  3. Douglas Wells

    Phrogz Guest

    Whoa, I've never seen that wording. That is entirely at odds with the
    way Ruby behaves; as you note, no whitespace stripping occurs, except
    that the '-' character allows the ENDDOC indicator to be indented.

    The lack of functionality that happens to be described in the document
    that you quote above is what caused me to add this RCR:
    http://www.rcrchive.net/rcrs/2
     
    Phrogz, Jan 25, 2007
    #3
  4. Douglas Wells

    Phrogz Guest

    Where is this document that you're referring to? I just checked my
    (win32 installer) version of Ruby 1.8.5, and I have no document named
    'syntax.html' anywhere in the tree of files.
     
    Phrogz, Jan 25, 2007
    #4
  5. It was installed on my local system (as part of the ports system
    on FreeBSD). A bit of spelunking shows that it is part of the
    'ruby-man' port. A bit more shows that it came as part of a tarball
    named ruby-man-1.4.6.tar.gz, indicating that it might be a bit
    long in the tooth. Checking the page on my systems, I see that
    it's fairly old, with the corresponding table of contents being
    dated February 1998.

    On the other hand, it appears to be the latest "Ruby reference
    manual" that I can find. A Google search for a "ruby reference
    manual" leads to
    http://www.ruby-doc.org/docs/ruby-doc-bundle/Manual/man-1.4/syntax.html#here_doc,
    which does contain the quoted text that I posted.

    - dmw
     
    Douglas Wells, Jan 26, 2007
    #5
  6. I vote for option 1 of the above proposal, since option 2 would break a lot of my current
    heredoc output.

    It would also be nice if one could specify how much of the END token leading spaces are
    removed (or replaced) from each line of the heredoc. Similar to the strip_output() method
    in... ri? (Can't remember exactly)

    That is, your

    class Foo
    def bar
    if whee
    print <<+END
    Hello World...
    Are you listening?
    END
    end
    end
    end

    produces

    Hello World...
    Are you listening?

    and then, for example,

    class Foo
    def bar
    if whee
    print <<+(2)END
    Hello World...
    Are you listening?
    END
    end
    end
    end

    produces

    Hello World...
    Are you listening?

    i.e. the leading spaces are replaced by the number specified after the +. (I'm lukewarm
    about the syntax, but you get the idea)

    I realise that would be equivalent to

    print <<+END
    Hello World...
    Are you listening?
    END

    but the "<<+(n)TOKEN" functionality would be a really nice feature because the number of
    indent spaces, n, can then be easily passed into methods interpolated in the heredoc that
    produce output you also want to be indented accordingly. I have that situation now where
    interpolated strings in heredocs are produced in the called method via another heredoc (I
    hope that makes sense.)

    cheers,

    paulv
     
    Paul van Delst, Jan 26, 2007
    #6
  7. Douglas Wells

    Phrogz Guest

    [snip additional suggestions and discussion of the RCR]

    I'm mighty tempted to ask you for some examples of what your current
    Heredoc output looks like and how the proposal would break it.
    (However, pretend that I didn't actually just type that.) Instead, I
    think that -- to support the RCR process -- I should probably ask you
    to create an account at RCRchive.net, subscribe to the mailing list for
    that RCR, and post your question again so that I can ask you questions
    there.
     
    Phrogz, Jan 26, 2007
    #7
  8. Douglas Wells

    Phrogz Guest

    Interesting. Definitely, as we've established, not correct information
    for the current version of Ruby.

    Is anyone around and listening who is old enough to remember 1.4, and
    to know if that is how indented heredoc strings worked back then? (I'm
    interested because it's very similar to my RCR, and I'd love to know
    the reason that the functionality was abandoned, if it was.)
     
    Phrogz, Jan 26, 2007
    #8
  9. Hi,

    At Sat, 27 Jan 2007 05:35:06 +0900,
    Phrogz wrote in [ruby-talk:236308]:
    Nothing has ever changed. The document is incorrect definitely.
     
    Nobuyoshi Nakada, Jan 27, 2007
    #9
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