Ivan Vilata i Balaguer wrote: > 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,
I'm afraid I'm still baffled. Are you saying that your proposal is necessary to preserve compatibility with Python versions before 2.3? Otherwise, it appears to introduce clutter with no clear benefit. I don't find Numexpr in NumPy, are you referring to a scipy module? Colin W. ------------------------------------------------------------------------- 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
