En/na Colin J. Williams ha escrit: > Ivan Vilata i Balaguer wrote: >> Hi all. The attached diff makes some changes to Numexpr support for >> booleans. The changes and their rationale are below. >> >> 1. New ``True`` and ``False`` boolean constants. This is so that 1 and >> 0 are always proper integer constants. It is also for completeness, >> but I don't envision any usage for them that couldn't be expressed >> without the constants. >> > I'm puzzled. > Python already has constants True and False of the bool type. bool is a > subclass of the int type. > Any instance of the bool type can be converted to the int type. > >>> a=1==0 > >>> type(a) > <type 'bool'> > >>> int(a) > 0 > >>> a > False > >>> > > Colin W. > >> 2. The only comparisons supported with booleans are ``==`` and ``!=``, >> so that you can compare boolean variables. Just as NumPy supports >> complex order comparisons and Numexpr doesn't, so goes for bools. >> Being relatively new, I think there is no need to keep >> integer-boolean compatibility in Numexpr. What was the meaning of >> ``True > False`` or ``2 > True`` anyway?
Well, the ``True`` and ``False`` constants where not previously
supported in Numexpr because they had to be defined somewhere. Now they
are.
Regarding the Python int and bool types and their relationships, it is a
very elegant solution introduced in Python 2.3 since previous versions
didn't have a proper boolean type, so the 0 and 1 ints where used for
that. What I'm proposing here is, since Numexpr has a recent story and
most probably there isn't much code affected by the change, why not
define the boolean type as a purely logical one and leave its numeric
compatibility issues out? By the way, it simplifies Numexpr's virtual
machine (less casting opcodes).
I admit again this looks a little baffling, of course, but I don't think
it would mean many noticeable changes to the user.
Regards,
::
Ivan Vilata i Balaguer >qo< http://www.carabos.com/
Cárabos Coop. V. V V Enjoy Data
""
signature.asc
Description: OpenPGP digital signature
------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
