William Martell <[EMAIL PROTECTED]> wrote:
:
: Hi Charles. Thank you very much for the code and the lesson.
: Works perfectly!
It wasn't meant to be a finished product. Just an example to
learn from. You need to, at least, add some error checking, but
I am glad it works. :)
: I am trying to add the address portion to this but I am still
: having some trouble. I wanted to see if I could ask you
: questions regarding your code for even more insight. Thanks
: in advance for your time and consideration.
No problem.
Please keep asking!
[ I edited the questions so they appeared under the code. ]
: # column names
: print csv( {
: date => 'Date',
: price => 'Price',
: bedrooms => 'Bedrooms',
: bathrooms => 'Bathrooms',
: living_areas => 'Living_areas',
: phone => 'Phone',
: address => 'Address',
: location => 'Location',
: arrangement => 'Arrangemant',
: paper => 'Paper', } ), "\n";
:
: (OK, right here, it looks like you just made things easier
: by not naming a hash and declaring the fields then printing
: via csv sub procedure, and instead just declared an
: anonymous hash, is this correct? )
Yes. An unnamed hash is called an anonymous hash.
I don't know if it is easier, but when I first started
Randal (I think?) said something about unnecessarily using
extra variables. Since, all this does is print out the
column names, it doesn't make sense to define a file scoped
variable for this one use.
:
: # Set field defaults
: %ad = (
: date => '',
: price => '',
: bedrooms => '',
: bathrooms => '',
: living_areas => '',
: phone => '',
: address => '',
: arrangement => '',
: location => '',
: paper => '',
: );
:
: (Here I am still a little foggy, but I think you are saying
: that in the hash %ad there are these keys and the default
: values in them are blank, if they get replaced with real
: values later in the program great, and if not, they will
: still print as blank. Is this correct?)
Yes. Though I would call "''", blank. Maybe an empty
or zero-length string, but blank sounds like it could have
spaces in it.
: while ( <DATA> ) {
:
: if ( /^Price/ ) {
:
: # add the last ad if it exists
: print csv( \%ad ), "\n" if is_valid_ad( \%ad );
.
.
.
: # update %ad for this line
:
: @ad{ qw| price bedrooms bathrooms living_areas | }
:
: (I am having trouble with this, I think you are using the
: array symbol because we are dealing with a list, but that
: the values held in $_ and returned by price_fields sub
: procedure will actually apply to the hash %ad,
: Is this correct??
Yes. It is called a slice. Read the section on slices in
'perldata'.
: = price_fields( $_ );
: }
: Another question is how does Perl know what $_ is
: referring to, I guess the line that begins with Price but
: I am not sure, please explain.)
while ( <DATA> ) {
is a short-cut for:
while ( defined( $_ = <DATA> ) ) {
Many programmers, especially on the list, emphasize that
we should use:
while ( defined( my $line = <DATA> ) ) {
And then operate on $line. In my haste, I got lazy. :)
Regardless, $_ (or $line) is set to the value of the
current line each time the loop begins.
HTH,
Charles K. Clarkson
--
Mobile Homes Specialist
254 968-8328
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