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Re[3]: How's your Perl?

by xmath (Hermit)
on Oct 27, 2003 at 06:36 UTC ( [id://302339]=note: print w/replies, xml ) Need Help??

in reply to Re: Re: How's your Perl?
in thread How's your Perl?

oops, you're right, my definition of "static" in the clarification was flawed :-)

I do mean function-scoped static like in C/C++ ofcourse

btw tachyon, your #1 solution isn't:
perl -le 'my @x = ( \$_, \$_ ); $x[0]=42; print $x[1]'

Replies are listed 'Best First'.
Re: Re[3]: How's your Perl?
by tachyon (Chancellor) on Oct 27, 2003 at 07:26 UTC

    Read your rules. You don't specify HOW the value of $x[0] is changed :-) vis Create an array @x such that changing $x[0] also sets $x[1] to the same value While assignment is one way to change a value....

    @x=(\$_,\$_); $_=10; print "\$x[$_] = ${$x[$_]}\n" for 0..$#x; $_=20; print "\$x[$_] = ${$x[$_]}\n" for 0..$#x; __DATA__ $x[0] = 10 $x[1] = 10 $x[0] = 20 $x[1] = 20

    cheers $[



      Create an array @x such that changing $x[0] ...

      @x=(\$_,\$_); my $initial_value = $x[0]; $_=10; print "\$x[$_] = ${$x[$_]}\n" for 0..$#x; die "But \$x[0] did not change.\n" if $x[0] eq $initial_value; $_=20; print "\$x[$_] = ${$x[$_]}\n" for 0..$#x; die "But \$x[0] did not change.\n" if $x[0] eq $initial_value;

      You're really printing the wrong thing.

      print "\$x[$_] = ${$x[$_]}\n" for 0..$#x; ^^ ^ LHS is $foo, RHS is $$foo. The output is very misleading. print "\${\$x[$_]} = ${$x[$_]}\n" for 0..$#x; LHS is $$foo and RHS is $$foo. But we're interested in $foo. print "\$x[$_] = $x[$_]\n" for 0..$#x; LHS is $foo and RHS is $foo. Output is correct and shows that the need +ed change did not happen.

      You're changing the variable that is refered to by the references in $x[0] and $x[1], but you're not actually changing the value in the container that is named $x[0].

      Clearer would be: "so that assigning to $x[0] also changes ...", but as said, we're against sanity.

      Juerd # { site => '', plp_site => '', do_not_use => 'spamtrap' }

        I agree that it was not what was expected but it does fulfill the criteria as stated. The answer was probably supposed to be this as noted elsewhere:

        $[ The index of the first element in an array, and of the first character + in a substring. Default is 0, but you could theoretically set it to +1 to make Perl behave more like awk (or Fortran) when subscripting an +d when evaluating the index() and substr() functions. (Mnemonic: [ be +gins subscripts.) As of release 5 of Perl, assignment to $[ is treated as a compiler dir +ective, and cannot influence the behavior of any other file. --> Its +use is highly discouraged :-) $[ = 1; $x[0] = 1; show(); $x[0] = 2; show(); $x[1] = 3; show(); sub show { print "\$x[$_] = $x[$_]\n" for 0..$#x; }




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