2. EL 6 ELS
  3. perl-PPI
  4. PPI::Token::HereDoc(3pm)

Scroll to navigation

PPI::Token::HereDoc(3) User Contributed Perl Documentation PPI::Token::HereDoc(3)

NAME

PPI::Token::HereDoc - Token class for the here-doc

INHERITANCE

  PPI::Token::HereDoc
  isa PPI::Token
      isa PPI::Element

DESCRIPTION

Here-docs are incredibly handy when writing Perl, but incredibly tricky when parsing it, primarily because they don't follow the general flow of input.

They jump ahead and nab lines directly off the input buffer. Whitespace and newlines may not matter in most Perl code, but they matter in here-docs.

They are also tricky to store as an object. They look sort of like an operator and a string, but they don't act like it. And they have a second section that should be something like a separate token, but isn't because a strong can span from above the here-doc content to below it.

So when parsing, this is what we do.

Firstly, the PPI::Token::HereDoc object, does not represent the "<<" operator, or the "END_FLAG", or the content, or even the terminator.

It represents all of them at once.

The token itself has only the declaration part as its "content".

  # This is what the content of a HereDoc token is
  <<FOO
  
  # Or this
  <<"FOO"
  
  # Or even this
  <<      'FOO'

That is, the "operator", any whitespace separator, and the quoted or bare terminator. So when you call the "content" method on a HereDoc token, you get '<< "FOO"'.

As for the content and the terminator, when treated purely in "content" terms they do not exist.

The content is made available with the "heredoc" method, and the name of the terminator with the "terminator" method.

To make things work in the way you expect, PPI has to play some games when doing line/column location calculation for tokens, and also during the content parsing and generation processes.

Documents cannot simply by recreated by stitching together the token contents, and involve a somewhat more expensive procedure, but the extra expense should be relatively negligible unless you are doing huge quantities of them.

Please note that due to the immature nature of PPI in general, we expect "HereDocs" to be a rich (bad) source of corner-case bugs for quite a while, but for the most part they should more or less DWYM.

Comparison to other string types

Although technically it can be considered a quote, for the time being "HereDocs" are being treated as a completely separate "Token" subclass, and will not be found in a search for PPI::Token::Quote or "PPI::Token::QuoteLike objects".

This may change in the future, with it most likely to end up under QuoteLike.

METHODS

Although it has the standard set of "Token" methods, "HereDoc" objects have a relatively large number of unique methods all of their own.

heredoc

The "heredoc" method is the authoritative method for accessing the contents of the "HereDoc" object.

It returns the contents of the here-doc as a list of newline-terminated strings. If called in scalar context, it returns the number of lines in the here-doc, excluding the terminator line.

terminator

The "terminator" method returns the name of the terminating string for the here-doc.

Returns the terminating string as an unescaped string (in the rare case the terminator has an escaped quote in it).

TO DO

- Implement PPI::Token::Quote interface compatibility

- Check CPAN for any use of the null here-doc or here-doc-in-s///e

- Add support for the null here-doc

- Add support for here-doc in s///e

SUPPORT

See the support section in the main module.

AUTHOR

Adam Kennedy <adamk@cpan.org>

COPYRIGHT

Copyright 2001 - 2009 Adam Kennedy.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

2009-08-08 perl v5.10.1