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Re: postfix dereference syntax

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Johan Vromans
August 15, 2013 18:11
Re: postfix dereference syntax
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demerphq <> writes:

> This aside I think there is a real problem with this proposal. It
> breaks the original model of sigils completely. IMO sigils are hard
> enough that completely breaking the original intent is not helpful, no
> matter how sweet your tooth is for the syntactic sugar it offers.
> My understanding of the Perl5 sigils is that they are meant to denote
> the type of result that will be _returned_*.
> We write:
>    $thing= $foo[1];
> and not
>    $thing= @foo[1];
> because the former tells us we are getting back a scalar. The latter
> says we are getting back a list.
> [...]
> * I looked for documentation to back this up, and the best I could
> find was in perlfaq4. I suspect that it is better documented in one of
> the Perl books by Larry.

From the first Camel:

  You'll note that we didn't have to tell Perl what kind of variable
  $answer is. That's because the $ character itself tells Perl that
  $answer can hold a single value, which can be either a string or a
  number. We call this a scalar variable.


  We use the $ in $ARRAY[SCALAR] to indicate that we are selecting a
  scalar value even though it's coming from an array that is named
  @ARRAY. That will be confusing to you until you discover that you can
  use @ in @ARRAY[LIST] as the notation for array slices, and you figure
  out that the $ or @ is controlling the context of the subscript.

Camel I didn't mention sigils, it called them "funny characters":

  Some consider that having the variables all start with funny
  characters makes Perl an ugly language. [...]

Camel IV was the first book to call them "sigils".

  Note that we do not have to be very specific about kind of variable
  $phrase is. The $ character tells Perl that phrase is a scalar
  variable, that is, one con- taining a singular value. An array
  variable, by contrast, would start with an @ character. [...] Perl has
  some other variable types, with unlikely names like “hash”, “handle”,
  and “typeglob”. Like scalars and arrays, these types of variables are
  also preceded by funny characters, commonly known as sigils.

Also, from Camel IV:

  Array subscripts are enclosed in square brackets [like this], so if
  you want to select an individual array element, you would refer to it
  as $home[n], where n is the subscript (one less than the element
  number) you want. See the example that follows. Since the element you
  are dealing with is a scalar, you always precede it with a $.

Note the last sentence. This is fundamental to Perl as we know it, and
also one of the fundamental differences between Perl and Perl6. 

-- Johan

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