Hash table threshold is now float, not double

Change default from 0.8 to 0.8125 so it fits in float without
rounding glitches.
* doc/lispref/hash.texi (Creating Hash):
* doc/lispref/objects.texi (Hash Table Type):
* etc/NEWS:
Document change.
* src/fns.c (make_hash_table, maybe_resize_hash_table)
(Fmake_hash_table): Threshold is now float, not double.
Be consistent about how this is rounded.
* src/lisp.h (struct Lisp_Hash_Table.rehash_threshold):
Change back to float, now that the other code rounds consistently.
(DEFAULT_REHASH_THRESHOLD): Now float 0.8125 instead of double 0.8.

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 143e4655def..9355dff7a08 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -904,6 +904,10 @@ consistency with the new functions.  For compatibility, 'sxhash'
 remains as an alias to 'sxhash-equal'.
 
 +++
+** 'make-hash-table' now defaults to a rehash threshold of 0.8125
+instead of 0.8, to avoid rounding glitches.
+
++++
 ** New function 'add-variable-watcher' can be used to call a function
 when a symbol's value is changed.  This is used to implement the new
 debugger command 'debug-on-variable-change'.