[Python-Dev] [Python-checkins] r64424 - in python/trunk:Include/object.h Lib/test/test_sys.py Misc/NEWSObjects/intobject.c Objects/longobject.c Objects/typeobject.cPython/bltinmodule.c (original) (raw)

Mark Dickinson dickinsm at gmail.com
Thu Jun 26 23:26:42 CEST 2008

On Thu, Jun 26, 2008 at 9:55 PM, Mark Dickinson <dickinsm at gmail.com> wrote:

It's disadvantage from Python's point of view is that some features are IEEE 754

Aargh! I can't believe I wrote that. Its. Its. Its. Anyway; some more detail:

Both C99 and Java 1.5/1.6 support hex floating-point literals; both in exactly the same format, as far as I can tell. Here are the relevant productions from the Java grammar:

HexDigit: one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F

HexNumeral: 0 x HexDigits 0 X HexDigits

HexDigits: HexDigit HexDigit HexDigits

HexadecimalFloatingPointLiteral: HexSignificand BinaryExponent FloatTypeSuffix_opt

HexSignificand: HexNumeral HexNumeral . 0x HexDigits_opt . HexDigits 0X HexDigits_opt . HexDigits

BinaryExponent: BinaryExponentIndicator SignedInteger

BinaryExponentIndicator:one of p P

Java's 'Double' class has a 'toHexString' method that outputs a valid hex floating point string, and the Double() constructor also accepts such strings.

C99 also appears to have full support for input/output of hex floats; e.g. using strtod and printf('%a', ...).

Not sure how helpful this is.

Mark

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