assignment expression peeve

[Alex Martelli]

Carl Banks wrote:
   ...
> The real reason is that assignment expressions lead to all kinds of
> ugly and unreadable code.  This is because there is no linguistic
> analogue for assignment as an expression.  Things that work as

"""
Once upon a time, in a Kingdom far, far away, there was a
strong, corageous prince, who we'll call Richard, and his weak,
cowardly, but cunning younger brother, who we'll call John,
secretly hated and feated Richard and envied his strength.
One day, Richard and John set out on a fateful hunt in the woods
...
"""

Those clauses "who we'll call Richard" and "who we'll call John"
are exact natural-language equivalents of assignment-as-expression
(in a computer language with reference, not copy, semantics, of
course - but Python qualifies in this regard), or as close as
anything in natural language ever gets to computer languages.

Basically, I'm parentethically affixing a name to some entity
I'm describing, just so I can later use the name, rather than
some periphrasis, or a pronoun, with the well-known problems
that these can cause (computer languages don't have pronouns,
unless you want to consider perl's $_ as such perhaps...:-).

Of course there are alternatives (aren't there always, most
particularly in natural language?), such as claiming that you're
just informing the reader of the prince's "actual" name (but if
the kingdom was so far away, it's believable that the prince's
actual name was too hard to pronounce for us and "Peter" is just
a pseudonym you're using for convenience;-) -- but values in
computer languages don't have "actual names", in this analogy,
just "pseudonyms" anyway.

I'm not necessarily dissenting with your detestation of
assignment-as-expression (although gradually I'm getting some
doubts about the general, overall wisdom of Python's strong
distinction between expressions and statements, that's a more
general and problematic issue).  But I _am_ dissenting with
your specific claim that "there is no linguistic analogue"
for it in natural language.


Alex