[cctbxbb] pyyaml - iotbx.pdb incompatibility

James Stroud xtald00d at gmail.com
Mon Apr 15 23:21:47 PDT 2013

On Apr 15, 2013, at 11:21 PM, Nathaniel Echols wrote:
> Is your example more or less what YAML does that triggers the crash?

Yes, the example I gave is essentially the YAML code distilled. For some reason yaml wants to make infs and nans. Here is around 256 of yaml/constructor.py:

    inf_value = 1e300
    while inf_value != inf_value*inf_value:   # ⇐ Line 256
        inf_value *= inf_value
    nan_value = -inf_value/inf_value   # Trying to make a quiet NaN (like C99).

But what they are doing really doesn't make any sense to do, because infs and nans can be made in python without all of the gymnastics:

    >>> inf_value == float('inf')
    >>> nan_value = flaot('nan')

I would agree that boost's trapping the conditional on line 256 is not a bug. If 1e300 * 1e300 were defined, they wouldn't "need" to use a loop to find the nan.


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