Ok, that make much more sense - I think. So, I guess, the outer 'if'
and 'else' statements get evaluated first. Then the inner 'if' can
proceed once all the lines of data were gathered in the outer 'else'
statement. This way the lines can be assigned as a key-value pair in
the hash. I guess the individual who wrote the code could make it much
cleaner or easier to read. The re-organizing of the conditionals in
your second e-mail makes it perfectly clear and would be something I
would have done had I known how the nested 'if' statement was working
(again if I have right). Hopefully, I 'got it' now. I can see why many
coders are annoyed with nested if statements. :-)
-Thanks!
-Mike
On Jul 3, 2004, at 4:38 AM, Randy W. Sims wrote:
On 7/2/2004 10:25 PM, Michael S. Robeson II wrote:
Well yeah, the indentation makes it much more clearer. However, this
does not help me understand how the nested "if" statements are
working. Which of the two "if" statements gets evaluated first? I am
trying to figure out "in english" what the "if" statements are
actually doing. Is it saying:
"If a line begins with ">bla-bla" and if $seq (which appears no
where else in the code other than " $seq="" ") exists assign it to
the hash "pro" with the name "bla-bla"."
So my question is how does the inner if statement work when seq="" is
out side that "if" statement?
Is the outer "if" statement evaluated first then the inner? Because
how does the inner "if" statement know what "$seq" is?
I am probably not making any sense but I am trying to figure out
mechanically how the perl interpreter knows what to do in the context
of the nested if statements.
Tidied up a little more:
my( %pro, @names);
my( $name, $seq, $k );
while (defined( my $line = <DATA> )) {
if ($line =~ /^>(.+)/) {
if ($seq) {
$pro{$name} = $seq;
$seq = '';
}
$name = $1;
$name =~ s/\s//g;
push @names, $name;
$k++;
} else {
chomp( $line );
$seq .= $line;
}
}
This code deals with multi-line sequences, putting multiple lines
together untill a sequence is complete. The 'else' part of the outter
'if' does the accumulation of multiple lines into a sequence. The 'if'
part determines that a sequence is complete, captures some type of
name from the sequence, stores the complete sequence in the '%pro'
hash, and pushes the name onto a '@names' array. I'm guessing '$k'
keeps tally of the number of sequences; it's not clear if that is
neccessary since `scalar @names` possibly will provide the same info.
It's also unclear why there is a '@names' array that mostly duplicates
`keys %pro`
I think where you're-understandably-getting confused is that most of
those variables are global. That's made more explicit in my
strictified rewrite above. It could probably be rewritten better if we
knew the exact format of the data being read.
Randy.
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