in reply to Use of uninitialized value in string eq

my @temp = $info{$humangi};

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assigns one value to @temp, so you'll have a problem if $position is anything other than 0.

By the way, the following very suspicious: 

my ($source, $position, $sink) = split(/(\d+)(\w)/, $Variant);

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Specifically, /(\d+)(\w)/ doesn't look like it would match a separator. It should probably be 

my ($source, $position, $sink) = $Variant =~ /(.*?)(\d+)(\w)/;

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Re^2: Use of uninitialized value in string eq
by sophix (Sexton) on Apr 21, 2010 at 21:31 UTC
    Hi ikegami, thanks for the reply.

    I do not see why there would be a problem with the assignment of one value to @temp. My intention was to put the protein sequence (of human gi) into an array and then to point a position in this sequence. I thought I would bump into the problem you mentioned in case I would have used $temp, and actually that's why I used an array there. I would be glad if you can tell me what might be the problem.

    Suspicious, indeed. Yet it is working properly. I first used (\w)(\d+)(\w) and then modified it as to have the current one following the errors I got. I guess it first makes a split as P and 82L and then makes a second split by separating 82 and L. Your alternative looks more appropriate to use though.

    Any idea concerning the use of 'eq' operator?

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      Any idea concerning the use of 'eq' operator?

      ikegami has already given you the answer to that. Your line

      my @temp = $info{$humangi};

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      assigns a single scalar value to element zero only of the @temp array and no other element is initialised, but your line

      my ($source, $position, $sink) = split(/(\d+)(\w)/, $Variant);

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      assigns the value of 82 to $position using your example of "P82L" in $Variant. Your comparison

      if ( $temp[$position] eq $source) {

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      attempts to access element 82 of @temp which does not exist, hence the warning.

      I hope this clarifies things for you.

      Cheers,

      JohnGG

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      I do not see why there would be a problem with the assignment of one value to @temp.

      What do you think $temp[82] returns when @temp only has one value? undef.

      I guess it first makes a split as P and 82L

      split is designed to split a separated list, but there's no separator between the fields in "P82L".

      Yet it is working properly.

      In the same sense that towing your car to work is a working alternative to driving to work.

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        Thank you John and ikegami. As I was afraid, it seems that I do still have difficulties with the basics of Perl (or rather of programming).

        So the problem seems to have started when I first read the sequence line as $info{$gi}=$line;.

        And then, @temp = $info{$humangi} operates as such $temp[0] = $info{$humangi}. I hope I get this right.

        Thus, a possible solution is to store the sequence into an array in the beginning. To be frank, I do not know how to do this. Alternatively, there might be a way to convert a scalar value to an array list. (I would use split but as I see from your last comment on the use of split function, this is not a good way to do it.

        Can you help me on this one?
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