Author loewis
Recipients Arfrever, christian.heimes, georg.brandl, loewis, mark.dickinson, meador.inge, ncoghlan, pitrou, python-dev, skrah, vstinner
Date 2012-08-10.17:47:09
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Message-id <50254916.2050400@v.loewis.de>
In-reply-to <20120810164643.GA21311@sleipnir.bytereef.org>
Content
> So v.format must equal w.format, where format is a format string in
> struct module syntax. The topic of this issue is to determine under
> what circumstances two strings in struct module syntax are considered
> equal.

And that is exactly my question: We don't need a patch implementing
it (yet), but a specification of what is to be implemented first.

I know when two strings are equal (regardless of their syntax):
if they have the same length, and contain the same characters in
the same order. Apparently, you have a different notion of "equal"
for strings in mind, please be explicitly what that notion is.

> memoryview can compare against any object with a getbufferproc, in this
> case array.array. memoryview_richcompare() calls PyObject_GetBuffer(other)
> and proceeds to compare its own internal Py_buffer v against the obtained
> Py_buffer w.

Can this be expressed on Python level as well? I.e. is it correct
to say: an array/buffer/memoryview A is equal to an object O iff
A is equal to memoryview(O)? Or could it be that these two equivalences
might reasonably differ?

> Hence my proposal to demand a strict canonical form for PEP-3118 format
> strings, which would be a proper subset of struct module format strings.

Can you kindly phrase this as a specification? Who is demanding what
from whom?

Proposal: two format strings are equal if their canonical forms
are equal strings. The canonical form C of a string S is created by ???

However, it appears that you may have something different in mind
where things are rejected/fail to work if the canonical form isn't
originally provided by somebody (whom?)

So another Proposal: two format strings are equal iff they are
in both in canonical form and are equal strings.

This would imply that a format string which is not in canonical
form is not equal to any other strings, not even to itself, so
this may still not be what you want. But I can't guess what it
is that you want.
History
Date User Action Args
2012-08-10 17:47:10loewissetrecipients: + loewis, georg.brandl, mark.dickinson, ncoghlan, pitrou, vstinner, christian.heimes, Arfrever, skrah, meador.inge, python-dev
2012-08-10 17:47:09loewislinkissue15573 messages
2012-08-10 17:47:09loewiscreate