All --
Dan asked me to remove the swap op, since what he really wants
is rotate. So, I implemented an initial version of rotate. Here's
the log entry:
* core.ops: Replaced 'swap()' by 'rotate(i|ic)'.
* stacks.c and stacks.h: Removed swap-related functions from my
prior commit, replacing them with stack_depth(), stack_entry()
and rotate_entries().
NOTE: The stack_depth() and rotate_entries() routines could
be made more efficient through the caching of the sum of chunk
'used' members from lower chunks in a field in the upper
chunks. Also, if the interpreter's stack_base was changed to
hold the pointer to the *top* chunk (since we usually come
at the stack from the top down) instead of the *bottom*
chunk. The code here at least works, and we can decide about
bigger changes separately.
For now, rotate only handles rotates in one direction and
of magnituded one. A fully general rotate would do handle
rotates in both directions and of arbitrary amounts. Again,
this implementation is sufficient for current applications,
and a feature-complete version can be developed if this turns
out to be otherwise the right type of implementation.
This change includes a new exception for ERROR_STACK_SHALLOW,
meaning "not-empty-yet-not-deep-enough-for-what-you-asked".
* jakoc: Changed the calling convention to use rotate instead
of swap (of course). Also changed the convention for return
value passing to use the stack as well.
Regards,
-- Gregor
