[Python-bugs-list] [ python-Feature Requests-445484 ] pickle lacks float('inf')

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Feature Requests item #445484, was opened at 2001-07-28 08:21
Message generated for change (Comment added) made by bcannon
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Category: None
Group: None
Status: Open
Resolution: Later
Priority: 4
Submitted By: Anthony Doggett (anthonydoggett)
Assigned to: Nobody/Anonymous (nobody)
Summary: pickle lacks float('inf')

Initial Comment:
Support for float('inf') still appears to be missing in

Python 2.1.1 (#1, Jul 28 2001, 14:15:01) 
[GCC egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)]
on linux2

>>> cPickle.dumps(float('inf'), 1)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
SystemError: frexp() result out of range
>>> pickle.dumps(float('inf'), 1)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/var/ajd111/python/lib/python2.1/pickle.py",
line 943, in dumps
    Pickler(file, bin).dump(object)
  File "/var/ajd111/python/lib/python2.1/pickle.py",
line 109, in dump
    self.save(object)
  File "/var/ajd111/python/lib/python2.1/pickle.py",
line 211, in save
    f(self, object)
  File "/var/ajd111/python/lib/python2.1/pickle.py",
line 273, in save_float
    self.write(BINFLOAT + pack('>d', object))
SystemError: frexp() result out of range


Both structmodule.c and cPickle.c require changes.
Surely something like 

  if (x == HUGE_VAL) {    /* Inf */
      e = 1024;
      f = 0.0;
  }
  else {
      f = frexp(x, &e);
      ...

and

  if (e == 1024)
      x = HUGE_VAL;		/* Inf */
  else {

is all that is required for all IEEE754 machines?

(structmodule.c requires similar changes for Float
also)

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>Comment By: Brett Cannon (bcannon)
Date: 2003-05-12 17:46

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PEP 754 should make sure to deal with this.

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Comment By: Tim Peters (tim_one)
Date: 2001-09-05 13:16

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Changed to Feature Request, and added to new "Non-
accidental 754 support" section of PEP 42.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-09-05 11:21

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Is there a point in keeping this bug report open
indefinitely? A "won't fix" would make just as much sense.
Maybe add Inf support to PEP 42.

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Comment By: Tim Peters (tim_one)
Date: 2001-08-01 15:41

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Note that Python has no intentional support for Infs and 
NaNs anywhere; even that float('inf') doesn't blow up when 
you do it is a platform accident (it blows up ("invalid 
literal") on my box).

Given that, in the absence of a comprehensive plan for 
supporting this stuff across the board, and worker bees to 
implement it, I downgraded the priority.  A good plan would 
refactor the code so that dealing with the platform double 
and float formats occurs in only one place.

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