TextIO.scanStream problems

[Stephen Weeks]

> We  knew  that  this was how scanStream worked: until the reader returns, the
> initial state is kept alive, and it is only dead then if the  reader  returns
> SOME  _  and  no  one  else  is  holding  on to it. 

I had never realized that.  I think it's horrible to the point of unusability
(as if the speed problems weren't already enough).

> I thought we had already
> discussed an implementation which was way way cheaper: the state consists  of
> a  buffer  and  an offset.  Each buffer contains a ref which points to either
> the next buffer or the end of the  line  (the  latter  including  the  actual
> things  you  need  to do I/O).  Thus you will keep the linked list of buffers
> around, but that is cheap space wise.  I.e., the space kept alive is  1  byte
> per char, the absolute minimum.

I don't remember discussing it.  Anyways, that's what I'm now implementing.