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Re: comparing strings
by davorg (Chancellor) on Oct 30, 2002 at 15:29 UTC
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for (0 .. $#lines1) {
print $lines1[$_] eq $lines2[$_] ? $lines1[$_] : '*';
}
--
<http://www.dave.org.uk>
"The first rule of Perl club is you do not talk about
Perl club."
-- Chip Salzenberg
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Re: comparing strings
by blokhead (Monsignor) on Oct 30, 2002 at 15:30 UTC
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It might be easier for you to use just strings rather than the overhead of arrays for this. Use the substr function to get the nth character in the sequence.
my $dna1 = 'CACTATGAGTGATCGC';
my $dna2 = 'ACTGACTAATGCGTTG';
print "$dna1\n$dna2\n";
for (0 .. length($dna1)-1) {
if (substr($dna1,$_,1) eq substr($dna2,$_,1)) {
print ' ';
} else {
print '*';
}
}
print "\n";
__END__
# prints this:
CACTATGAGTGATCGC
ACTGACTAATGCGTTG
**** ** * *****
Also, there are quite a few problems in your original code. First, the value that you want to loop/iterate over is the number N when you are looking at the Nth character. But the foreach loop will set $base to each of the values in @lines1 and then to all the values in @lines2. You cannot get a pair of elements from two different arrays using a foreach loop. Also note that inside the loop, you are comparing the first elements of the array each time. You want to compare a different pair of elements each time through the loop. Lastly, @lines1[0] is invalid (at least until Perl6), and what you need to say instead is $lines1[0].
HTH and keep trying!
blokhead | [reply]
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Thanks blokhead,
But I am still having a few problems... I incorporated the
snippet you gave me which works fine apart from it doesn't
print the correct no. of *'s to correspond to the number of
mismatches!
This is what i did its slightly different from yours.
for ($dna_counter = 0; $dna_counter < $length_dna ; $dna_counter++ ) {
if (substr(@lines, $_, 1) eq substr (@lines2, $_, 1)) {
print '';
}
else {
print "*";
}
}
print "\n";
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Of course, if you're using arrays, you just need
if ($lines{$_] eq $lines2[$_]) {
The following will replace the non-matching chars in the string $str1 with "*" (and leave the matching chars) by converting $str2 to a regex:$str2 =~ s/./(?:($&)|.)/g;
print map{$_||'*'} $str1 =~ /$str2/
p | [reply]
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This is what i did its slightly different from yours.
...
if (substr(@lines, $_, 1) eq substr (@lines2, $_, 1))
...
Well, that's actually way different from
what Blockhead was doing -- he was using "substr()"
on a scalar ($line); substr() is not supposed to be used
on an array (@lines).
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Re: comparing strings
by termix (Beadle) on Oct 30, 2002 at 15:23 UTC
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I think getting one scalar out of a pair of arrays is going to give you one list (rather than the pair you want to compare). You can try this by adding a print $base line right inside the loop and seeing how many times it loops. Also, unless lines1 is an array of arrays, you want to get your character from it through a scalar like $lines1[0].
Depending on how good you are with perl you might find the following alternate too simple (or too c-like) but the foreach loop can replace the for loop (I think). And I never liked shifting.
# e.g @lines1 contains CACTATGAGTGATCGC and @lines2 contains
# ACTGACTAATGCGTTG.
@lines1= split(//,"CACTATGAGTGATCGC");
@lines2= split(//,"ACTGACTAATGCGTTG");
$line1length=@lines1;
$line2length=@lines2;
print ("1 :",@lines1,"\n");
print ("2 :",@lines2,"\n");
if ($line1length!=$line2length) {
print "Length Mismatch\n";
} else {
print "M :";
for ($x=0;$x<$line1length;$x++) {
if ($lines1[$x] eq $lines2[$x]) {
print $lines1[$x];
} else {
print "*";
}
}
print "\n";
}
--
termix | [reply]
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(tye)Re: comparing strings
by tye (Sage) on Oct 30, 2002 at 19:14 UTC
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my $line1= "CACTATGAGTGATCGC";
my $line2= "ACTGACTAATGCGTTG";
my $diff= $line1 ^ $line2; # Do a bit-wise xor
$diff =~ tr/\0-\xff/ */; # Change zero bytes to " ", others
+to "*"
print "$line1\n$diff\n$line2\n";
which prints
CACTATGAGTGATCGCG
* ************
GACTGACTAATGCGTTG
I'm not certain it would be a good fit for you, though.
- tye (/me shifts his cart into "overgolf") | [reply]
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Re: comparing strings
by artist (Parson) on Oct 30, 2002 at 15:47 UTC
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Hi,
Try this 'compact' version if the lengths are similar.
@lines1= split(//,"CACTATGAGTGATCGC");
@lines2= split(//,"ACTGACTAATGCGTTG");
@array = map { $lines1[$i++] eq $_ ? $lines1[$i-1] : '*' } @lines
+2;
print join "",@array;
Artist | [reply]
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Re: comparing strings
by Aristotle (Chancellor) on Oct 30, 2002 at 15:28 UTC
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I'll assume your arrays contain a single character per element, though that's unclear from your description.
while(@lines1 > 0 and @lines2 > 0) {
last if shift(@lines1) ne shift(@lines2);
}
print "*\n" if @lines1 > 0 or @lines2 > 0;
Makeshifts last the longest. | [reply]
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