Re: To be a list or not

[Stephen J. Turnbull]

Tom Tromey writes:
 > >>>>> "Stephen" == Stephen J Turnbull <address@hidden> writes:
 > 
 > Stephen> But please call it `true-list-p', which is the name of the
 > Stephen> similar XEmacs built-in.
 > 
 > Here's one stab at it.  This is basically lifted from safe-length.

Looks very familiar.

XEmacs implements one change you might think about.  Specifically, it
delays starting the tortoise until the length is "long enough to
suspect circularity".  I don't know if the value chosen was tuned or
not.  As I understand it, this makes the function slightly faster for
shorter lists, slightly slows down longer true lists, and might double
the detection time for cyclical lists.

Looks like a win to me, but YMMV.