[clug-progsig] Perl array disorder

[Shawn]

William???? Is that you??? Wasn't sure you were still kicking around.... 
:)  Good to see ya back!

Shawn

William Astle wrote:
> Royce Souther wrote:
>> I don't think I would call this a bug but more just another joke Larry Wall
>> is try to play on Perl programmers.
>>
>> I am working with a custom config file that looks kind of like badly
>> formated XML in that each field may contain any number of entries and
>> sub-entries. I stack the data into an array and when I go to pull the data
>> back out is is in a different order then when I put it in. This is not a
>> problem because the oder of the data is not important as long as the
>> hierarchy remains intact. I would like to know if there is a reason for
>> this. At some point in the future I may want an array in order and I should
>> know what needs to be done to make that way.
>>
>> root at QtCompiler[~] #cat ./PerlArrayDisorder.pl
>> #!/usr/bin/perl
>> #
>>
>> my @TestArray;
> 
> This makes @TestArray, an array.
> 
>> $TestArray->{'1'} = "one";
>> $TestArray->{'2'} = "two";
>> $TestArray->{'3'} = "three";
>> $TestArray->{'4'} = "four";
> 
> The above adds entries to a hash that is referenced by the scalar
> $TestArray.
> 
>> foreach $key (keys %{$TestArray})
>> {
>>         print "key=$key, value = ".$TestArray->{$key}."\n";
>> }
> 
> The above iterates over the keys in the hash referenced by the scalar
> $TestArray.
> 
>> root at QtCompiler[~] #./PerlArrayDisorder.pl
>> key=4, value = four
>> key=1, value = one
>> key=3, value = three
>> key=2, value = two
>>
>>
> 
> Your problem is that you are using *hashes*, not *arrays*. Arrays are
> indexed by [] while hashes are indexed by {}.
> 
> Your code actually has three things in it: an array that is declared
> local but never used, a scalar called $TestArray, and an anonymous hash
> (which $TestArray contains a reference to).
> 
> The following is approximately what you thought you were doing:
> 
> #!/usr/bin/perl
> my @TestArray;
> push (@TestArray, "one");
> push (@TestArray, "two");
> push (@TestArray, "three");
> push (@TestArray, "four");
> foreach $value (@TestArray)
> {
> 	print "$value\n";
> }
> 
> Note that arrays are indexed from 0.
> 
> push() adds an element to the end of the array.
> 
> $#TestArray would return the highest index in the array. That would be 3
> in the above example. (Indexes that exist would be 0, 1, 2, 3).
> 
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