The description of the %a/%A specifiers in the printf(3) man page
could stand some improvement. In particular, it is not clear from the
current document what base is used for the "p±d" part of the format.
It can be inferred from the nature of %a that the base should be
a power of two. and it can be further inferred from the nature of
hexadecimal floating-point literals in C (as specified by C99 and
later) that the base must exactly be the number two, but it would be
helpful for the printf(3) man page to state this explicitly. My first
expectation when reading the man page was that the exponent would be
taken in base 16; after experimentation my second thought is that it
is base FLT_RADIX (which is 2 on IEEE 754 floating-point systems, but
16 on S/390). Only by going back to the standard [1] could I determine
that the exponent in p-notation must always be taken from a base of 2.
[1] POSIX.1-2024
<https://pubs.opengroup.org/onlinepubs/9799919799/functions/printf.html>
Signed-off-by: Ken Pizzini <ken@xxxxxxx>
---
man/man3/printf.3 | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/man/man3/printf.3 b/man/man3/printf.3
index 7a96ec9c7..acabb3c3a 100644
--- a/man/man3/printf.3
+++ b/man/man3/printf.3
@@ -767,8 +767,11 @@ .SS Conversion specifiers
.IR double .
The digit before the radix point is unspecified for nonnormalized
numbers, and nonzero but otherwise unspecified for normalized numbers.
-The exponent always contains at least one
-digit; if the value is zero, the exponent is 0.
+The exponent,
+.IR d ,
+which is the appropriate exponent of 2 expressed as a decimal integer,
+always contains at least one digit;
+if the value is zero, the exponent is 0.
.TP
.B c
If no
--
2.47.0
