En Tue, 28 Apr 2009 09:22:01 -0300, Colin J. Williams <c...@ncf.ca>
escribió:
Lie Ryan wrote:
Aaron Brady wrote:
This makes it so all objects except False, None, 0, and empty
containers are true by default. I am not convinced that 'if <a
generic object>' should have any meaning; it should probably throw an
exception. Is it part of Python's look and feel or its mentality? Is
it part of the Zen? Certainly other ideal types can't be cast from
generic objects, so why booleans? Is it an ineffable component of the
author's vision for the language? I think that giving arbitrary
syntactic constructs meaning is just space-filler. It's worse than
syntactic sugar, it's semantic sugar. Why not assign meanings willy-
nilly to other random juxtapositions of tokens?
It's part of the design decision. In almost all cases (in any
language), a so-called "Design Decision" is rather random and prone to
subjective judgment, just as the decision to make bool(int) returns
False only on 0, -1, or for all negative values; whether to make
bool(100) and exception or True; or round() rounds down or up or
even-odd; or the use of brackets vs. indentation; or whether to treat
empty list as True or False.
I'm puzzled by the last sentence:
bool(0)
False
bool(-1)
True
bool(-100)
True
That's the "design decision". bool(-1) *might* have been False, and
bool(-100) *might* raise an exception. They behave the way they do because
of a conscious decision.
To Aaron: "Programming language design is not a rational science. Most
reasoning about is is at best rationalization of gut feelings, and at
worst plain wrong."
(GvR in python-ideas:
http://groups.google.com/group/python-ideas/msg/ac61f03c32578bae )
--
Gabriel Genellina
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