bltinmodule.c (original) (raw)

Guido van Rossum guido at python.org
Sat Jun 28 01:04:44 CEST 2008

On Fri, Jun 27, 2008 at 2:54 PM, Mark Dickinson <dickinsm at gmail.com> wrote:

On Fri, Jun 27, 2008 at 8:02 PM, Guido van Rossum <guido at python.org> wrote:

Now that I've learned about the hex float format supported by C++ and Java, I wonder if it wouldn't be better to support conversion to and from that format and nothing else.

E.g.

math.tohex(3.14) '0x1.91eb851eb851fp+1' math.fromhex('0x1.91eb851eb851fp+1') 3.1400000000000001 This would certainly be enough for me, though I think there's still some educational value in having binary output available. But that's just a matter of substituting a four-bit binary string for each hexadecimal digit (or learning to read hexadecimal as though it were binary).

If it's educational it can be left as an exercise for the reader. :-)

In fromhex, what would be done with a string that gives more hex digits than the machine precision can support? An obvious answer is just to round to the nearest float, but since part of the point of hex floats is having a way to specify a given value exactly, it might make more sense to raise an exception rather than changing the value by rounding it.

Whatever Java and C99 do.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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