On 2021-10-25 3:31 p.m., Mike Miller wrote:
> "defer" please.
>
> This construct did not happen in the past, and it's shorter of course.
>
> -Mike
>
I also like `defer`:
> def range(a, min=0, max = defer len(a)):
> return a[min:max]
`default` is also nice:
> def range(a, min=0, max default len(a)):
> return a[min:max]
I was concerned with this proposal at first because an inner function
definition may be ambiguous:
> def do_work():
> a = ['this', 'is', 'a', 'list']
> def range(a, min=0, max = defer len(a)):
> return a[min:max]
which `a` does `len(a)` refer to?
Looking through my code, it seems this is not a problem; outer method
variables rarely conflict with inner method parameters in practice.
Can deferred defaults refer to variables in scope? Can I use this to
evaluate arguments lazily?
> def coalesce(a, b):
> def _coalesce(x = defer a(), y = defer b()):
> if x is None:
> return x
> return y
> _coalesce()
>
>
> def expensive_method():
> return 84
>
>
> print(coalesce(lambda: 42, expensive_method))
Thank you
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