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Re: Using smart matching to find whether an array contains a string

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Aristotle Pagaltzis
January 26, 2011 04:37
Re: Using smart matching to find whether an array contains a string
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* Ed Avis <> [2011-01-26 13:15]:
> Thanks. In my original code the array is of strings so I could
> use this. But when I dropped into the command line to test
> behaviour with some one-liners, I reflexively picked (1, 2, 3)
> as my example array.
> This is a slightly unperlish distinction; usually in Perl it
> doesn't matter whether a scalar holds the number 42 or the
> string '42' - you can use either of them in arithmetic or
> string operations with the same semantics and no warnings. This
> is a contrast to languages like Python where you have a visible
> difference between numeric and string objects. Smart matching
> might be the first everyday case where the difference between
> numbers and strings becomes obvious to the ordinary Perl
> programmer.

Yes. I consider it to be exposing implementation details of Perl.

The very idea of smart matching fundamentally clashes with Perl 5
on this point, since it is supposed to look at the type of its
argument to figure out what kind of comparison operator to use to
establish boolean truth. Scalars are typeless in intent, though
not entirely in practice, and smart matching is left to figure
out a way to pick between two sets of operators. It’s kind of
insane, since any operation can affect the apparent type of
a scalar as a side effect. So ultimately the only sane way to use
smart matching is to use some literal value on the right-hand
side, never any program input.

Aristotle Pagaltzis // <>

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