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PEP 285: Adding a bool type

David Eppstein eppstein at ics.uci.edu
Sat Mar 30 13:04:17 EST 2002 
In article <a84t0v$k7u$1 at inputplus.demon.co.uk>,
 ralph at inputplus.demon.co.uk (Ralph Corderoy) wrote:

> > > Not in Guido's eyes <wink>.  We don't need 3 equivalent ways to
> > > turn an arbitrary expression into a bool ("bool(x)" same-as "not
> > > not (x)" same-as "truth(x)").  *Especially* if str(bool) and
> > > repr(bool) produce 'True' and 'False', people have a legitimate
> > > need to make an arbitrary true/false expression produce 0 and 1
> > > too, if only to preserve 0/1-based true/false output.
> > > operator.truth() has always been the best way to do exactly that.
> > > Alternatives like "(boolexpr) + 0" and "(boolexpr) and 1 or 0" and
> > > "(0, 1)[boolexpr]" reek in comparison.
> > 
> > Tim must be missing something.  The obvious way to turn a bool b into
> > an int is int(b).  Having to import the obscure 'operator' module for
> > this purpose is backwards.  (IMO there's almost *never* a reason to
> > import that module anyway.)
> 
> I thought Tim was trying to map a range of integer values onto just 0
> and 1 as ints, not False and True, where as you're suggesting he just
> wants to get an int from a boolean.  I think he has an expression like
> day_of_month, e.g. 30, and wants a 0 or 1 from it.
> 
> I could easily be wrong here.

If that's what he's doing, int(bool(x)) is still much clearer than the 
alternative bool-to-int expressions that (as he says) reek.

-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/
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