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.

2 files changed, 4 insertions, 3 deletions

diff --git a/doc/lispref/hash.texi b/doc/lispref/hash.texi
index 725d19c3bdc..4ba3258d189 100644
--- a/doc/lispref/hash.texi
+++ b/doc/lispref/hash.texi
@@ -144,8 +144,9 @@ The default value is 1.5.
 This specifies the criterion for when the hash table is full (so
 it should be made larger).  The value, @var{threshold}, should be a
 positive floating-point number, no greater than 1.  The hash table is
-full whenever the actual number of entries exceeds this fraction
-of the nominal size.  The default for @var{threshold} is 0.8.
+full whenever the actual number of entries exceeds the nominal size
+multiplied by an approximation to this value.  The default for
+@var{threshold} is 0.8125.
 @end table
 @end defun
 
diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi
index fbb66582f29..56049af60a1 100644
--- a/doc/lispref/objects.texi
+++ b/doc/lispref/objects.texi
@@ -1251,7 +1251,7 @@ and contents, like this:
 @example
 (make-hash-table)
      @result{} #s(hash-table size 65 test eql rehash-size 1.5
-                             rehash-threshold 0.8 data ())
+                             rehash-threshold 0.8125 data ())
 @end example
 
 @noindent