Delimited text - how find last index

[Kropotkin46]

Hi,
I'm returning to Lazarus after many years.  Used to drive Pasal, TurboPascal, Delphi and Lazarus but the  skills have faded.

Problem: need to split a string into words  as in eg perl 'split'.

I've failed with SplitString, tried lots od magicspells and none worked.

I stole some online code which showed promise but I can't work out how to terminate the iteration.

The example below at least compiles ok but the 'MyLast' shows as -1, hoping for 3, possibly 4. 
And the ugly repetition of the identifier 'MyList' seems to show that I'm missing a clue!

Help please?  A fix to find the end of the list should be easy but I've spent hours chasing it. 'WordCount' didn't help, either.

A completely different solution would be very welcome.

Using Lazarus (how find verson, no Help|About?) and FPC 3.2.2 on Linux Mint 22.3, 64bit

Code: [Select]


program SplitProg.pas;

uses Classes, StrUtils;
var MyList          : TStringList;
    MyIndex, myLast : Integer;
    MyDelim         : Char = ',';
begin
  MyList := TStringList.Create;
  MyList.Delimiter := ',';
  MyList.StrictDelimiter := True; // Ensures only ',' splits
  MyList.DelimitedText := 'one,two,three,four';

  // MyList[0] = 'one', MyList[1] = 'two', etc.

  WriteLn ( 'MyLast := ', MyList.LastIndexOf(MyList.DelimitedText) );

//for  MyIndex :=  0 to myLast do
// Writeln (MyList[MyIndex]);

  MyList.Free;

end.   



[Fibonacci]

Code: Pascal  [Select][+][-]

1. uses SysUtils;
2.  
3. var
4.   text: string;
5.   splitted: TStringArray;
6.   x: integer;
7.  
8. begin
9.   text := 'one,two,three,four';
10.   writeln('text = ', text);
11.  
12.   splitted := text.Split([',']); // array of separators
13.  
14.   writeln('items = ', length(splitted));
15.   x := high(splitted);
16.   writeln('index of last = ', x);
17.   writeln('last item = ', splitted[x]);
18. end.

[Remy Lebeau]

Problem: need to split a string into words  as in eg perl 'split'.

And, what do you want to do with it after you have split it?

I've failed with SplitString, tried lots od magicspells and none worked.

What exactly did you try that didn't work for you?

I stole some online code which showed promise but I can't work out how to terminate the iteration.

What do you mean by "terminate"? Stop a loop through the list? Use a Break statement.

The example below at least compiles ok but the 'MyLast' shows as -1

Of course it does, because you are searching the split list for the entire original delimited text rather than searching for a specific word in the list.

And the ugly repetition of the identifier 'MyList' seems to show that I'm missing a clue!

You can use a with statement.

Help please?

Help with WHAT, exactly? What is the GOAL you are trying to accomplish?

A fix to find the end of the list should be easy but I've spent hours chasing it. 'WordCount' didn't help, either.

MyList.Count tells you how many strings are in the list.

MyList.Count-1 tells you the index of the last string in the list.

MyList.LastIndexOf() tells you the index of the last matching string in the list.

[Zvoni]

Quick 'n dirty

Code: Pascal  [Select][+][-]

1. program SplitProg;
2. {$mode ObjFPC}{$H+}
3. uses Classes;
4. var MyList          : TStringList;
5.     MyIndex, myLast : Integer;
6.     MyDelim         : Char = ',';
7.     FirstWord, LastWord:String;
8. begin
9.   MyList := TStringList.Create;
10.   MyList.Delimiter := MyDelim;
11.   MyList.StrictDelimiter := True; // Ensures only ',' splits
12.   MyList.DelimitedText := 'one,two,three,four';
13.  
14.   FirstWord:=MyList[0];
15.   LastWord:=MyList[MyList.Count-1];
16.  
17.   WriteLn('FirstWord='+FirstWord);
18.   WriteLn('LastWord='+LastWord);
19.  
20.   MyList.Free;
21.   Readln;
22. end.

[Kropotkin46]

Problem: need to split a string into words  as in eg perl 'split'.

And, what do you want to do with it after you have split it? 
 
*** Parse through the incoming NEC2 card, details at https://www.nec2.org/part_3/toc.html.

I've failed with SplitString, tried lots od magicspells and none worked.

What exactly did you try that didn't work for you?
*** Lots, can't remember all of them.

I stole some online code which showed promise but I can't work out how to terminate the iteration.

What do you mean by "terminate"? Stop a loop through the list? Use a Break statement.

*** 'for ..to'  needs to know a definite  final value for 'to'.  I thought ' terminate the iteration' was clear.  Apparently not.

The example below at least compiles ok but the 'MyLast' shows as -1

Of course it does, because you are searching the split list for the entire original delimited text rather than searching for a specific word in the list.

*** I am trying to find the index of the last word, I don't know in advance what word to search for.  I could add a delimiter word to the end of the list?

And the ugly repetition of the identifier 'MyList' seems to show that I'm missing a clue!

You can use a with statement.

**** OK!  I'd forgotten that possibility.

Help please?

Help with WHAT, exactly? What is the GOAL you are trying to accomplish?

*** I'm trying to write an optimiser for an antenna design - specifically the 40m and 15m element of my DX Commander Signature 9.  Also keeping in mind the possibility of a more-general optimiser.  And yes, such an optimiser exists but I can't get it to install, never mind it isn't designed for what I want.

A fix to find the end of the list should be easy but I've spent hours chasing it. 'WordCount' didn't help, either.

MyList.Count tells you how many strings are in the list.

MyList.Count-1 tells you the index of the last string in the list.

MyList.LastIndexOf() tells you the index of the last matching string in the list.

[Kropotkin46]

Code: Pascal  [Select][+][-]

1. uses SysUtils;
2.  
3. var
4.   text: string;
5.   splitted: TStringArray;
6.   x: integer;
7.  
8. begin
9.   text := 'one,two,three,four';
10.   writeln('text = ', text);
11.  
12.   splitted := text.Split([',']); // array of separators      //foo.pas(12,20) Error: Illegal qualifier  //Fatal: Compilation aborted
13.  
14.   writeln('items = ', length(splitted));
15.   x := high(splitted);
16.   writeln('index of last = ', x);
17.   writeln('last item = ', splitted[x]);
18. end.

[Kropotkin46]

Quick 'n dirty

Code: Pascal  [Select][+][-]

1. program SplitProg;
2. {$mode ObjFPC}{$H+}
3. uses Classes;
4. var MyList          : TStringList;
5.     MyIndex, myLast : Integer;
6.     MyDelim         : Char = ',';
7.     FirstWord, LastWord:String;
8. begin
9.   MyList := TStringList.Create;
10.   MyList.Delimiter := MyDelim;
11.   MyList.StrictDelimiter := True; // Ensures only ',' splits
12.   MyList.DelimitedText := 'one,two,three,four';
13.  
14.   FirstWord:=MyList[0];
15.   LastWord:=MyList[MyList.Count-1];
16.  
17.   WriteLn('FirstWord='+FirstWord);
18.   WriteLn('LastWord='+LastWord);
19.  
20.   MyList.Free;
21.   Readln;
22. end.

Thank you, that worked!

[paweld]

But before you retrieve the values, check whether TStringList contains any elements, e.g.

Code: Pascal  [Select][+][-]

1.   if MyList.Count > 0 then
2.   begin
3.     FirstWord := MyList[0];
4.     LastWord := MyList[MyList.Count - 1];
5.   end
6.   else
7.   begin
8.     FirstWord := '';
9.     LastWord := '';
10.     ShowMessage('List is empty!');
11.   end;

[Zvoni]

But before you retrieve the values, check whether TStringList contains any elements, e.g.

Code: Pascal  [Select][+][-]

1.   if MyList.Count > 0 then
2.   begin
3.     FirstWord := MyList[0];
4.     LastWord := MyList[MyList.Count - 1];
5.   end
6.   else
7.   begin
8.     FirstWord := '';
9.     LastWord := '';
10.     ShowMessage('List is empty!');
11.   end;

Nice defensive programming.
But you are not accounting for a failed split (e.g. "wrong" delimiter)

Since he assigned to Stringlist.Text/DelimitedText, there IS at least one entry

So, i'd rather go with

Code: Pascal  [Select][+][-]

1.   FirstWord := MyList[0];  //This one MUST exist, irrespective if the split was successful or not
2.   LastWord := '';
3.   if MyList.Count > 0 then LastWord := MyList[MyList.Count - 1];

[paweld]

Since he assigned to Stringlist.Text/DelimitedText, there IS at least one entry

If you pass an empty string, the list will remain empty and

Code: Pascal  [Select][+][-]

1. FirstWord := MyList[0];  //This one MUST exist, irrespective if the split was successful or not

will return an AccessViolation

[Zvoni]

Since he assigned to Stringlist.Text/DelimitedText, there IS at least one entry

If you pass an empty string, the list will remain empty and

Code: Pascal  [Select][+][-]

1. FirstWord := MyList[0];  //This one MUST exist, irrespective if the split was successful or not

will return an AccessViolation

Hmm....True enough

[VisualLab]

The line with the program keyword was missing. Just complete the code:

Code: Pascal  [Select][+][-]

1. program SplittingText;
2.  
3. uses
4.   SysUtils;
5.  
6. var
7.   AnyText: string;
8.   SplittedText: TStringArray;
9.   AIndex: integer;
10.  
11. begin
12.   AnyText := 'one,two,three,four';
13.   WriteLn('text = ', AnyText);
14.   SplittedText := AnyText.Split([',']); // array of separators
15.   WriteLn('items = ', length(SplittedText));
16.   AIndex := High(SplittedText);
17.   WriteLn('index of last = ', AIndex);
18.   WriteLn('last item = ', SplittedText[AIndex]);
19.   ReadLn;
20. end.

Tested in Lazarus 4.6 (Windows 11, 64-bit).

[Thaddy]

@VisualLab

The program line is optional and not required in Freepascal.
Freepascal ignores it.
Example:

Code: Pascal  [Select][+][-]

1. //full program
2. begin
3. end.

 

[Aruna]

The example below at least compiles ok but the 'MyLast' shows as -1, hoping for 3, possibly 4. 

This has been answered by others am just trying to shed some light on why this happens.
The problem: MyList.LastIndexOf(MyList.DelimitedText)
MyList.DelimitedText = 'one,two,three,four' (the whole string)

But your list contains:

Code: Pascal  [Select][+][-]

1. "one'
2. 'two'
3. 'three'
4. 'four'
5.  

So it tries to find 'one,two,three,four' inside the list → not found → returns -1

That’s why you get -1.

The simple fix :
Use .Count instead:

Code: Pascal  [Select][+][-]

1. myLast := MyList.Count - 1;
2. WriteLn('MyLast := ', myLast);
3.  
4. for MyIndex := 0 to myLast do
5.   WriteLn(MyList[MyIndex]);

Output:

Code: Pascal  [Select][+][-]

1. MyLast := 3
2. one
3. two
4. three
5. four

Using Lazarus (how find verson, no Help|About?) and FPC 3.2.2 on Linux Mint 22.3, 64bit

I have attached a zip file for you to test and play with. Have fun. The attached screenshot shows you this  in action.

[Remy Lebeau]

'for ..to'  needs to know a definite  final value for 'to'.  I thought ' terminate the iteration' was clear.  Apparently not.

If you are going to iterate through a TStringList using indexes then you would use the TStringList.Count property as the final value, eg:

Code: Pascal  [Select][+][-]

1. var i: Integer;
2. for i := 0 to myList.Count-1 do

Alternatively, you can use a for..in loop instead (if you don't need the indexes for anything else):

Code: Pascal  [Select][+][-]

1. var s: string;
2. for s in myList do

I am trying to find the index of the last word, I don't know in advance what word to search for.

Then TStringList.Count-1 is what you are looking for.