Re: [gobo-eiffel-develop] indenting text output filter

[Eric B. <er...@go...>]

Andreas Leitner wrote:
> Hi all:
> 
> I have been generating a lot of code over the years. Printing
> indentation was always a messy issue. It involved lots of unreadable '%
> T's.  I very much liked Eric's approach in gec where you have a tripple
> of rouintes (one for increasing indentation, one for decreasing and one
> for printing the current level).
> 
> I have generalized this approach now for Erl-G into an output filter. It
> is a class that you put in front of your actual text output stream. This
> class _is_ an outputstream with the two additional public commands of
> `indent' and `detent' (better names welcome!) and transparently prints
> indentation for every line to a given target output stream.
> 
> I have attached the class as it might be useful to others. Eric if you
> like it please feel free to include it in Gobo.

I'm just trying to find a better name. If it *is* an output stream,
then it is not a filter. What about KL_INDENTED_TEXT_OUTPUT_STREAM
(should it really be in the kernel library, or elsewhere (where?))?
Or should the indentation facility be part of KI_TEXT_OUTPUT_STREAM
with an option to enable it or not? In fact we probably don't need
an option, the fact that `indent' is never called (and hence
`indentation' is kept to 0) should be enough. The questions are:
is it acceptable to add 2 attributes to class KI_TEXT_OUTPUT_STREAM,
and will the test to figure out that there is actually no indentation
to be printed be noticeable in terms of performance?

Note your implementation is not bullet-proof. It won't work if we
call `put_string' with an argument that contains newlines. Is that
acceptable? If yes, it should be clearly stated.

-- 
Eric Bezault
mailto:er...@go...
http://www.gobosoft.com