"[EMAIL PROTECTED]" <[EMAIL PROTECTED]> writes: > Fredrik Lundh wrote: >> x = "10" + 20 # should this be 30 or 1020 or "1020" or ...? >> > I think Perl handles this case pretty well and sane. > > In fact, this strict but dynamic type checking is quite painful to work > with, especially the new decimal class. > > I can do a : > > decimal + int > > but not > > decimal + float > > But then when I use some built-in math functions, it can convert > decimal to float and return a float which then cannot be operate with > another decimal.
Interesting probllem. Decimal + float can't return a decimal - we don't do implicit conversion from float to decimal, because there's no obvious correct conversion. So decimal.__add__ returns NotImplemented, which I believe is the correct thing to do. IIRC, this defers the operation to the float type. Float doesn't handle implicit conversion to anything but but builtin types. In particular, it doesn't check to see if the object beinng added has a __float__ method, and invoke that to do the conversion if it does. This looks like a bug. Either decimal.__add__ should return a float in these circumstances (not pretty), or float should check for the __float__ attribute and deal with it. On the other hand, the secton in the manual says that in Python 3.0 coercion won't be supported, so this may be a reflection of how things are going to be in the future. <mike -- Mike Meyer <[EMAIL PROTECTED]> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. -- http://mail.python.org/mailman/listinfo/python-list
