Question

I’m looking for the conversion from the PHP code to Delphi. Currently, i’m stuck when handling with the Isset() function in PHP code. Are there any way i can convert the below code into Delphi ?

$collection = array(
'doc1' =>'php powerbuilder',
'doc2' =>'php visual'); 
$dictionary = array();
$docCount = array();    
foreach ($collection as $docID => $doc) {
        $doc = strtolower($doc);
        $terms = explode(' ', $doc);
        $docCount[$docID] = count($terms);
        foreach ($terms as $term) {
            if (!isset($dictionary[$term])) {
                $dictionary[$term] = array('df' => 0, 'postings' => array());
            }

            if (!isset($dictionary[$term]['postings'][$docID])) {
                $dictionary[$term]['df']++;
                $dictionary[$term]['postings'][$docID] = array('tf' => 0);
            }
            $dictionary[$term]['postings'][$docID]['tf']++;
        }
    }

Answer 1

PHP arrays are, according to the documentation, a one-size-fits-all data structure that works as an ordered list or as a hash map (dictionary). Delphi does not have a similar built in data structure, you can only get either vector (ordered list) behavior, or hash map / dictionary behavior. And the dictionary behavior is only easily accessible on Delphi 2009+ because that’s the version that introduced Generics.

The easy to use data structure that’s available on Delphi 2007 and can be used for inset type of operations is the TStringList, in it’s Sorted := True mode. But this is no true dictionary, it’s just a sorted list of strings where each string can have a value associated with it. You would use it like this:

procedure Test;
var L: TStringList;
begin
  L := TStringList.Create;
  try
    L.Sorted := True; // make the list "Sorted" so lookups are fairly fast
    L.AddObject('doc1', SomeData); // SomeData can't be string, it needs to be TObject descendant
    L.AddObject('doc2', SomeOtherData);
    if L.IndexOf('doc3') = -1 then // this is equivalnt to the `inset` test
    begin
      // doc3 is not in list, do something with it.
    end;
  finally L.Free;
  end;
end;

This of course is not a complete answer, but should get you started.