On Tue, Apr 11, 2006 at 01:46:05PM +0200, felix winkelmann wrote: > On 4/10/06, Dan <[EMAIL PROTECTED]> wrote: > > Hi all, > > > > After reading the SRFI-40 (stream library) egg > > documentation at > > > > http://www.call-with-current-continuation.org/eggs/srfi-40.html > > > > I thought that the implementation includes the srfi-45 > > fixes to avoid space leaks. However, the test program > > below seems to take up an ever-increasing amount of > > memory. What gives? > > > > Hm. I don't use streams much, but since you are referencing > the 5-gazillionth element, you probably have to build the > list up to that element, or not?
He is looping through the elements with a tail-recursive function. This should not pose any problems, since only the car of the list needs to be forced, after which it is discarded and recursion takes place on the cdr. I don't completely understand everything in SRFI-45, but it looks like the implementation of stream-unfoldn (used by stream-filter) should use lazy instead of delay? If I understand correctly, delay and force are not "fixed" by SRFI-45, but the algorithm of converting a program to a lazy version of the program is "fixed" by requiring lazy instead of delay. HTH, Peter -- http://www.student.ru.nl/peter.bex -- "The process of preparing programs for a digital computer is especially attractive, not only because it can be economically and scientifically rewarding, but also because it can be an aesthetic experience much like composing poetry or music." -- Donald Knuth
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