Harold Castro wrote: > > #This line is too tricky for me, all I know is that it > has a ternary hook operator which returns $_ if the > expression my @fields = map length() is true, > otherwise, substitute empty fields with 'NA'. I looked > into perldoc -f map as well as length() and as far as > I can only understand, an empty argument pass to > length will make use of $_. While the 'map' as used in > example on perldoc would translate a list of numbers > to their corresponding character using this line: > > @chars = map(chr, @nums); > > > Would you mind explaining me how did you tell it to > substitute empty cells with 'NA' using the line below? > I just can't seem to find any sort of like this > substitution using, 's/ /NA/g' > > my @fields = map length() ? $_ : 'NA', split /:/, $_, > -1;
Assuming you start with the contents of $_ being: "four:five:\n" chomp() on the first line removes the newline so you are left with: "four:five:" split( /:/, $_, -1 ) splits the contents of $_ using the colon (:) as the separator and returns the list: ( 'four', 'five', '' ) * note that without the negative number as the third argument it would only return the list ( 'four', 'five' ), the negative number ensures that *all* fields are returned. map() processes each member of the list separately through a local copy of the $_ variable and passes the result through to the assignment. Inside the map() the expression: length() ? $_ : 'NA' tests the string length of $_ and if it is zero it returns the string 'NA' or else it returns the contents of $_. HTH John -- use Perl; program fulfillment -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] <http://learn.perl.org/> <http://learn.perl.org/first-response>
