On Wed, Jul 8, 2020 at 7:23 PM Rob Cliffe <[email protected]> wrote:
> *Use '==' to mark* (when necessary) *load-and-compare items*:
> match t:
> case (==USE_RECT, real, imag):
> return complex(real, imag)
> case (==USE_POLAR, r, phi):
> return complex(r * cos(phi), r * sin(phi))
>
> allowing incidentally a possible future extension to other relational
> operators:
> case Point(x, >YMAX):
> case >= 42:
>
The problem with this is that value patterns don't just appear at the top
level.
Consider this example from the PEP's deferred ideas section:
case BinaryOp(left=Number(value=x), op=op, right=Number(value=y)):
Using your notation, this would become:
case BinaryOp(left=Number(value===x), op===op,
right=Number(value===y)):
The tokenizer, which is eager, would interpret '===' as '==' followed by
'=' and it would treat this as a syntax error. Also, it looks a lot like a
JavaScript equivalency (?) operator.
A single '=' prefix suffers from pretty much the same thing -- Python's
tokenizer as well as the tokenizer in most people's heads would read
'x==op' as containing '=='.
Please drop it.
--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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