Python Dev <[email protected]> wrote:
+10. See
https://stackoverflow.com/questions/36825925/expressions-with-true-and-is-true-give-different-results/36826262#36826262
for concrete evidence where another semantically inconsistent
operator overloading caused trouble and what Stroustroup has to
say on the matter.
On 31.07.2020 13:42, Larry Hastings wrote:
On 7/31/20 12:36 AM, Tobias Kohn wrote:
And since pattern matching is really
a new feature to be introduced to Python, a feature that can
be seen in different lights, there is no 'Python-Programmer
intuition' that would apply in this case.
It's not fair to say "intuition doesn't apply because it's new
syntax". There are plenty of examples of intuition serving a
Python programmer well when encountering new syntax. A Python
programmer's intuition is informed by existing syntax and
conventions in the language. When they see a new construct,
its similarity to existing constructs can make understanding
the new syntax quite intuitive indeed.
Take for example list comprehensions. Python 1 programmers
hadn't seen
a = [x for x in y]
But they knew what square brackets meant in that context, it
meant "creates a new list". And they knew what "for x in y"
meant, that meant iteration. Understanding those separate two
concepts, a Python 1 programmer would be well on their way to
guessing what the new syntax meant--and they'd likely be
right. And once they understood list comprehensions, the
first time they saw generator expressions and set and dict
comprehensions they'd surely intuit what those did immediately.
The non-intuitiveness of PEP 622, as I see it, is that it
repurposes what looks like existing Python syntax but
frequently has wholly different semantics. For example, a
"class pattern" looks like it's calling a function--perhaps
instantiating an object?--but the actual semantics and
behavior is very different. Similarly, a "mapping pattern"
looks like it's instantiating a dict, but it does something
very different, and has unfamiliar and seemingly arbitrary
rules about what is permitted, e.g. you can't use full
expressions or undotted-identifiers when defining a key. Add
the "capture pattern" to both of these, and a Python
programmer's intuition about what this syntax traditionally
does will be of little help when encountering a PEP 622 match
statement for the first time.
Cheers,
//arry/
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--
Regards,
Ivan
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