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5.7 Comments
============

One of the most common forms of escape sequence is the comment.(1)
(*note Comments-Footnote-1::)

 -- Escape sequence: \"
     Start a comment.  Everything up to the next newline is ignored.

     This may sound simple, but it can be tricky to keep the comments
     from interfering with the appearance of the output.  If the escape
     sequence is to the right of some text or a request, that portion of
     the line is ignored, but spaces preceding it are processed normally
     by GNU 'troff'.  This affects only the 'ds' and 'as' requests and
     their variants.

     One possibly irritating idiosyncrasy is that tabs should not be
     used to vertically align comments in the source document.  Tab
     characters are not treated as separators between a request name and
     its first argument, nor between arguments.

     A comment on a line by itself is treated as a blank line, because
     after eliminating the comment, that is all that remains.

          Test
          \" comment
          Test
              => Test
              =>
              => Test

     To avoid this, it is common to combine the empty request with the
     comment escape sequence as '.\"', causing the input line to be
     ignored.

     Another commenting scheme sometimes seen is three consecutive
     single quotes (''''') at the beginning of a line.  This works, but
     GNU 'troff' emits a warning diagnostic (if enabled) about an
     undefined macro (namely '''').

 -- Escape sequence: \#
     Start a comment; everything up to and including the next newline is
     ignored.  This 'groff' extension was introduced to avoid the
     problems described above.

          Test
          \# comment
          Test
              => Test Test

 -- Request: .ig [end]
     Ignore input until, in the current conditional block (if any),(2)
     (*note Comments-Footnote-2::) the macro END is called at the start
     of a control line, or the control line '..' is encountered if END
     is not specified.  'ig' is parsed as if it were a macro definition,
     but its contents are discarded, not stored.(3)  (*note
     Comments-Footnote-3::)

          hand\c
          .de TX
          fasting
          ..
          .ig TX
          This is part of a large block of input that has been
          temporarily(?) commented out.
          We can restore it simply by removing the .ig request and
          the call of its end macro.
          .TX
              => handfasting