Your version doesn't preserve any of the lines that are read:
: readln-skipcomments ( -- )
[ { [ string? ] [ first CHAR: # = not ] [ ] } 1&& ] [ readln ] do
while ;
If you want the last line (the one where predicate is false and breaks out
of the loop), you could put an object on the stack to test against, like
this:
: readln-skipcomments ( -- line )
f [ dup { [ string? ] [ first CHAR: # = not ] [ ] } 1&& ] [ drop
readln ] do while ;
The "do" will drop the ``f``, and then read a line. The predicate will run
and leave a boolean whether to continue or not.
On Fri, Jan 2, 2015 at 2:36 PM, Mark Green <m...@antelope.nildram.co.uk>
wrote:
> Hi,
>
> Sorry to post yet again! I've been trying to write something to read lines
> from a file while ignoring comments, and have gotten this far:
>
> : readln-skipcomments ( -- line )
> [ { [ string? ] [ first CHAR: # = not ] [ ] } 1&& ] [ readln ] do
> while ;
>
> The problem is that it seems that while consumes the result of running
> pred, so this ends up not returning anything. If I put a dup into the last
> entry in the 1&&, to leave an extra copy on the stack in case of success,
> then I get a deep error complaining that the stack effect of the inputs of
> 1&&'s internal ifs are unbalanced. If I put the dup after the 1&& in the
> while I get an error that pred is unbalanced. If I put it in the looped
> quotation I get the error that the loop is not balanced by pred. Is there
> any way I can do this?
>
> Mark
>
>
>
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