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Subject Author Date
Help: Reverse Letters Amy Lee 05-02-2008
Posted by Jürgen Exner on May 2, 2008, 11:15 am
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>>>There's a problem while I'm processing sequences. My file content.
>>>ATGCCCTGACGTAAACGTAGGCTACG
>>>And I hope I can reverse the sequences to be this.
>>>GCATCGGATGCAAATGCAGTCCCGTA
>>
>> You asked a self answering question: The reverse() function does exactly
>> that.
>>
>>>I use "reverse" to do this, but it dose not work any more.
>>
>> ?????
>> Are you saying that coming back into the office after yesterday's Labour
>> Day the functionality of reverse() in Perl has changed?
> unless (/^>.*$/)
> {
> reverse $_;
> }

Had you used
        use warnings; use strict;
as it strongly recommended then perl itself would have told you:

        "Useless use of reverse in void context at [...] line [...]."

In other words: You reverse the content of $_ and then throw it away.

jue

Posted by RedGrittyBrick on May 2, 2008, 10:52 am
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 Amy Lee wrote:
> Hello,
>
> There's a problem while I'm processing sequences. My file content.
>
>> seq1
> ATGCCCTGACGTAAACGTAGGCTACG
>> seq2
> GCATGCCCTACGGGTACCCCAGTA
>
> And I hope I can reverse the sequences to be this.
>
>> seq1
> GCATCGGATGCAAATGCAGTCCCGTA
>> seq2
> ATGACCCCATGGGCATCCCGTACG
>
> I use "reverse" to do this, but it dose not work any more.
> So could you tell me how to solve this problem?
>

reverse needs a list

$ perl -e '$x="GCAT";$y=join"",reverse(split "",$x);print"$y\n"'
TACG

doubtless there are better ways to do this.

--
RGB

Posted by RedGrittyBrick on May 2, 2008, 10:55 am
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RedGrittyBrick wrote:
> Amy Lee wrote:
>> Hello,
>>
>> There's a problem while I'm processing sequences. My file content.
>>
>>> seq1
>> ATGCCCTGACGTAAACGTAGGCTACG
>>> seq2
>> GCATGCCCTACGGGTACCCCAGTA
>>
>> And I hope I can reverse the sequences to be this.
>>
>>> seq1
>> GCATCGGATGCAAATGCAGTCCCGTA
>>> seq2
>> ATGACCCCATGGGCATCCCGTACG
>>
>> I use "reverse" to do this, but it dose not work any more.
>> So could you tell me how to solve this problem?
>>
>
> reverse needs a list
>
> $ perl -e '$x="GCAT";$y=join"",reverse(split "",$x);print"$y\n"'
> TACG
>

Oh no it doesn't! How embarassing.

perl -e '$x="GCAT";$y=reverse($x);print"$y\n"'
TACG

--
RGB

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