In perl.git, the branch blead has been updated
<http://perl5.git.perl.org/perl.git/commitdiff/6ce229987d0f9e304395547fb10685bb677a7e5c?hp=60d5033292df238895c866316ce2f72eb76e3bb9>
- Log -----------------------------------------------------------------
commit 6ce229987d0f9e304395547fb10685bb677a7e5c
Author: Jarkko Hietaniemi <j...@iki.fi>
Date: Sun Jul 17 14:58:19 2016 +0300
VAX: further docs about the VAX fp formats
-----------------------------------------------------------------------
Summary of changes:
perl.h | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/perl.h b/perl.h
index c6c18db..4a6c4f1 100644
--- a/perl.h
+++ b/perl.h
@@ -6779,9 +6779,20 @@ extern void moncontrol(int);
* The ordering of the parts in VAX floats is quite vexing.
* In the below the fraction_n are the mantissa bits.
* The fraction_1 is the most significant (numbering as by DEC/Digital),
- * and the rightmost bit in each fraction is the least significant.
- * This means for example that both the the most and least significant
- * bits are in the middle of the floats, not at either end.
+ * while the rightmost bit in each fraction is the least significant:
+ * in other words, big-endian bit order within the fractions.
+ * The fraction segments themselves would be big-endianly, except that
+ * within 32 bit segments the less significant comes first, the more
+ * significant after, except that in the format H (used for long doubles)
+ * the first fraction segment is on its own. As promised, vexing.
+ * This means for example that both the most and the least significant
+ * bits can be in the middle of the floats, not at either end.
+ *
+ * References:
+ * http://nssdc.gsfc.nasa.gov/nssdc/formats/VAXFloatingPoint.htm
+ * http://www.quadibloc.com/comp/cp0201.htm
+ * http://h71000.www7.hp.com/doc/82final/6443/6443pro_028.html
+ * (somebody at HP should be fired for the URLs)
*
* F fraction_2:16 sign:1 exp:7 fraction_1:7
* (exponent bias 128)
@@ -6790,7 +6801,7 @@ extern void moncontrol(int);
* fraction_4:16 fraction_3:16
* (exponent bias 128)
*
- * G fraction_2:16 sign:1 exp:11 fraction_1:7
+ * G fraction_2:16 sign:1 exp:11 fraction_1:4
* fraction_4:16 fraction_3:16
* (exponent bias 1024)
*
--
Perl5 Master Repository
