[% setvar title Alternate Syntax for variable names %]
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Alternate Syntax for variable names
Maintainer: David Corbin <dcorbin@machturtle.com> Date: 20 Aug 2000 Last Modified: 28 Aug 2000 Mailing List: perl6-language@perl.org Number: 133 Version: 2 Status: Developing
Many new users are confused by the use of $@% to represent context, when it is also used to declare variables. This is a syntactic change that introduces a bit more logic to the context/type confusion.
Context is an essential part of Perl. When evaluating a symbolic
expression, $, @ and % are used to indicate the context of the
expression. However, when variables are declared (using local, my, or
simply implicitly as an lvalue) these same symbols are used. my
@array; my %hash; $var=1
To many people, most notably programmers new
to Perl, the $@% is mistakenly believed to be part of the variable
name. This leads to such erroneous attempts to use them as
@array[0]
, and @%hash{key}
.
Consider the following syntax:
my var; # declaring a scalar my array[]; # declaring an array my hash{}; # declaring a hash
Then, when it is necessary to distinguish context explicitly (it often is not), you can use $@% as before. Consider:
count = array; # scalar context because of assignment to scalar. alt_array[] = array; # list context value = hash{key}; # print $array," ",@array #Context must be clearly designated.
I'm not the linguist that Mr. Wall is, but it strikes me that context should be derrived automatically as much as possible.
An slightly different alternative would be that arrays and hashes are always referred to with their trailing indicator ([] or {}). So, from the example above, you'd have
count=array[]; alt_array[] = array[];
Unknown.
RFC 9: Highlander Variable Types
RFC 109: Less linenoise - let's get rid of @%