Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: eryk sun <eryksun@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Well, I finally ran into a Python Unicode problem, sort of
Date: Sun, 3 Jul 2016 23:46:26 +0000
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On Sun, Jul 3, 2016 at 6:58 AM, John Ladasky <john_ladasky@sbcglobal.net> w=
rote:
> The nabla symbol (=E2=88=87) is used in the naming of gradients. Python i=
sn't having it.
> The interpreter throws a "SyntaxError: invalid character in identifier" w=
hen it
> encounters the =E2=88=87.

Del is a mathematical operator to take the gradient. It's not part of
the name. For `=E2=88=87f`, the operator is `=E2=88=87` and the function na=
me is `f`.
Python lacks a mechanism to add user-defined operators. (R has this
capability.) Maybe this feature could be added. To make parsing
simple, user-defined operators could be limited to non-ASCII symbol
characters (math and other -- Sm, So). That simple option is off the
table if we allow symbol characters in names.

Adding an operator to the language itself requires a PEP. Recently PEP
465 added an `@` operator for matrix products. For example:

    >>> x =3D np.array([1j, 1])
    >>> x @ x
    0j
    >>> x @ x.conj() # Hermitian inner product
    (2+0j)

Note that using a non-ASCII operator was ruled out:

http://legacy.python.org/dev/peps/pep-0465/#choice-of-operator