I have a TStringList in Delphi.
after the items are inserted i call .sort procedure to sort the items.
the Items are first names followed by last names. for example: "John Smith".
I want to sort the items by last name. I mean by the first character after the space.
how can I do this?
and also the items may be unicode strings like persian characters.
I'd use the CustomSort method of TStringList to supply a custom compare function. First of all, let's imagine that we have already got the compare function:
function NameCompareFunc(List: TStringList; Index1, Index2: Integer): Integer;
begin
Result := ...;
end;
This function will (in due course) return negative to mean less than, positive to mean greater than and zero to mean equal.
Then we sort the list like this:
List.CustomSort(NameCompareFunc);
So, that's the easy bit done. But how do we implement NameCompareFunc? First of all let's split the name into last name and the rest.
procedure SplitName(const Name: string; out Last, Rest: string);
var
P: Integer;
begin
P := Pos(' ', Name);
if P = 0 then begin
Last := Trim(Name);
Rest := '';
end else begin
Last := Trim(Copy(Name, P+1, MaxInt));
Rest := Trim(Copy(Name, 1, P-1));
end;
end;
This is a pretty naive way to split a name. You'd probably want to search for separators starting from the end of the name, but I'll let you decide how to do that.
Now we can implement the compare function:
function NameCompareFunc(List: TStringList; Index1, Index2: Integer): Integer;
var
Last1, Last2, Rest1, Rest2: string;
begin
SplitName(List[Index1], Last1, Rest1);
SplitName(List[Index2], Last2, Rest2);
Result := AnsiCompareText(Last1, Last2);
if Result = 0 then begin
Result := AnsiCompareText(Rest1, Rest2);
end;
end;
Some notes:
I'm assuming that name comparison should always be case-insensitive.
We use AnsiCompareText to perform locale aware comparison.
If we encounter two names that have the same last name, then we implement a secondary comparison o the rest of the name.
You could use the CustomSort methos of Stringlist:
function LastNameCompareStrings(List: TStringList; Index1, Index2: Integer): Integer;
var
S1, S2: string;
SpaceIndex: Integer;
begin
S1 := List[Index1];
SpaceIndex := Pos(' ', S1);
if SpaceIndex <> 0 then
S1 := Copy(S1, 1, SpaceIndex - 1);
S2 := List[Index2];
SpaceIndex := Pos(' ', S2);
if SpaceIndex <> 0 then
S2 := Copy(S2, 1, SpaceIndex - 1);
if List.CaseSensitive then
Result := AnsiCompareStr(S1, S2)
else
Result := AnsiCompareText(S1, S2);
end;
procedure TForm7.ButtonFirstNameClick(Sender: TObject);
begin
NameBuffer.Sort;
Memo1.Lines.Assign(NameBuffer);
end;
procedure TForm7.ButtonLastNameClick(Sender: TObject);
begin
NameBuffer.CustomSort(#LastNameCompareStrings);
Memo1.Lines.Assign(NameBuffer);
end;
I my example I have all your names in a StringList called NameBuffer. Then I've added two buttons to a form where I sort mylist, and display the result on the Screen.
You could iterate through each item of your StringList (lets call it FullNames),
split each string and put the "splits" in two new separate stringlists which you could call
FirstNameList and LastNameList.
Now create a third stringlist which you can call ReverseFirstLast,
and combine the items from LastNameList with FirstNameList and put them in ReverseNames.
Now you have all names in reverse order. Last name first, and first name last.
You can now sort the ReverseFirstLast-list and do a split&combine method again to reverse orders again and maintain the sorting.
That is one way to do it to get a rough method up and running.
Related
I've attempted to implement a merge sort for strings however I cannot perform the recursive part and I get the error "Invalid Pointer Operation"
program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;
var i : Integer;
const MyArray : array[1..5]of string = ('hi', 'zebra', 'apple', 'Xylophone', 'dog');
Procedure merge(result, left, right : array of string);
var i, i1, i2 : Integer;
begin
i1 := 0;
i2 := 0;
for i := 0 to Length(result) do
begin
if (i2 >= Length(right)) or (i1 < Length(left)) and (StrComp(PChar(left[i]), PChar(right[i2])) < 0) then
begin
result[i] := left[i1];
inc(i1);
end
else
begin
result[i] := right[i2];
inc(i2);
end;
end;
end;
Procedure mergeSort(OriginalList : array of string);
var left, right : array of string;
i : Integer;
begin
if (Length(OriginalList) >= 2) then
begin
setlength(left, length(OriginalList) div 2);
setlength(right, length(OriginalList) - (length(OriginalList) div 2));
for i := 0 to Length(left) do
begin
left[i] := OriginalList[i];
end;
for i := 0 to Length(right) do
begin
right[i] := OriginalList[i + Length(OriginalList) div 2];
end;
mergeSort(left);
mergeSort(right);
merge(OriginalList, left, right);
end;
end;
begin
writeln('The data before sorting: ');
for i := low(MyArray) to High(MyArray) do
begin
write(MyArray[i]+' ');
end;
writeln;
mergeSort(MyArray);
writeln('The data before sorting: ');
for i := low(MyArray) to High(MyArray) do
begin
write(MyArray[i]+' ');
end;
readln;
end.
On the line in the mereSort function where I recall the merge sort function on the arrays "left" and "right", I get the error message but I don't quite understand why?
There are many different things wrong with this, hopefully these points will help you in the right direction.
Problems with Array Indexes
You are indexing beyond the end of your arrays:
Dynamic arrays are indexed starting from zero so the line
for i := 0 to Length(left) do
should be
for i := 0 to Length(left) - 1 do
or you can use
for i := Low(left) to High(left) do
As you did later.
I would recommend you choose a standard form and use it consistently, and also that you avoid declaring constant arrays with non-zero based indexing unless you have good reason, this way you can use the same forms consistently or change the type of array later without running into trouble
This first fix will stop your program crashing, but you'll notice your sort code isn't changing anything...
Problems with parameter passing
Delphi has several different ways to pass parameters into procedures:
procedure doSomething(a : array of string);
procedure doSomething(var a : array of string);
procedure doSomething(out a : array of string);
procedure doSomething(const a : array of string);
These determine how what happens inside the procedure can affect the original variable passed
This is something you will need to understand, read up in the documentation:
http://docwiki.embarcadero.com/RADStudio/Tokyo/en/Parameters_(Delphi)
There is IMO some very confusing behaviour and syntax relating to array parameters and a lot of stuff that seems intuitive is not allowed especially with XE/older version, its worth reading the documentation about the standard data types
In the current state, your merge procedure will have no effect because it only operates on a new copy of the array you pass in, which you have also declared as constant
Other
I would avoid the use of result as a procedure parameter since this is the name used for function return values, it seems like asking for trouble to use it like that.
PS: I haven't looked at the logic of the merging, just the basic language mistakes
I have some files in a directory. I try get these files with FindFirst and FindNext but I can't get same order on Windows 7.
C:\Test
SampleFile.0.png
SampleFile.1.png
SampleFile.2.png
SampleFile.3.png
SampleFile.4.png
SampleFile.5.png
SampleFile.6.png
SampleFile.7.png
SampleFile.8.png
SampleFile.9.png
SampleFile.10.png
SampleFile.11.png
SampleFile.12.png
SampleFile.13.png
SampleFile.14.png
SampleFile.15.png
SampleFile.16.png
SampleFile.17.png
SampleFile.18.png
SampleFile.19.png
SampleFile.20.png
SampleFile.21.png
SampleFile.22.png
When I try using my code I've got
SampleFile.0.png
SampleFile.1.png
SampleFile.10.png
SampleFile.11.png
SampleFile.12.png
SampleFile.13.png
SampleFile.14.png
SampleFile.15.png
SampleFile.16.png
SampleFile.17.png
SampleFile.18.png
SampleFile.19.png
SampleFile.2.png
SampleFile.20.png
SampleFile.21.png
.
.
.
How can I get file list on correct rank order?
Procedure Test;
var
sr : TSearchRec;
i : integer;
ListFiles : TStringList;
begin
ListFiles := TStringList.Create;
i := FindFirst('c:\test\*.png', faDirectory, sr);
while i = 0 do begin
ListFiles.Add(ExtractFileName(sr.FindData.cFileName));
i := FindNext(sr);
end;
FindClose(sr);
end;
Note : Result is still wrong, if I can use ListFiles.Sorted = True
I think I've a solution, created a function.
function SortFilesByName(List: TStringList; Index1, Index2: Integer): integer;
var
FileName1, FileName2: String;
i, FileNumber1, FileNumber2: Integer;
begin
FileName1 := ChangeFileExt(ExtractFileName(List[Index1]), '');
FileName2 := ChangeFileExt(ExtractFileName(List[Index2]), '');
i := POS('.', FileName1)+1;
FileNumber1 := StrToInt(Copy(FileName1, i, MaxInt));
i := POS('.', FileName2)+1;
FileNumber2 := StrToInt(Copy(FileName2, i, MaxInt));
Result := (FileNumber1 - FileNumber2);
end;
I've added another line
ListFiles.CustomSort(SortFilesByName); //(ListFiles,1,2):integer);
before
FindClose(sr);
As jachguate said, the sorting is done by Explorer.exe, not the filesystem. FindFirst/FindNext does not guarantee any specific sorting, including plain ASCII based, so you shouldn't rely on it. You don't, however, need to re-implement the numeric sort in Delphi. Windows exposes the one it uses as StrCmpLogicalW, which is in shlwapi.dll. The import looks like this:
function StrCmpLogicalW(psz1, psz2: PWideChar): Integer; stdcall;
external 'shlwapi.dll'
It is possible to disable that behavior in Windows. If you want to follow the order that Windows uses, you need to call SHRestricted with the REST_NOSTRCMPLOGICAL value. If it returns true you should use AnsiCompareStr instead.
const
// Use default CompareString instead of StrCmpLogical
REST_NOSTRCMPLOGICAL = $4000007E;
function SHRestricted(rest: DWORD): LongBool; stdcall; external 'shell32.dll';
So your final sort function should be something like this:
function CompareFilenames(const AFilename1, AFilename2: string): Integer;
begin
if SHRestricted(REST_NOSTRCMPLOGICAL) then
Result := AnsiCompareStr(AFilename1, AFilename2)
else
Result := StrCmpLogicalW(PWideChar(AFilename1), PWideChar(AFilename2));
end;
You can cache the result of the SHRestricted call, but if you do you need to watch for the WM_SETTINGSCHANGE broadcast message and re-read it when you get one.
The different orders you see in the windows explorer is implemented in explorer.exe and not in the file system.
The Numerical sort order is a new feature in windows 7, so if you sort by name and you have a bunch of files with a prefix followed by numbers, the explorer "identifies" that pattern and doesn't present a list sorted by name in the traditional way, but sorted by prefix and then by number (as if the string were a Integer number).
If you want to do the same in Delphi, you can do it by adding all the file names returned by FindFirst/FindNext to a TSlist and then sort the string list using this compare function:
var
FileNames: TList<string>;
begin
FileNames := TList<string>.Create;
try
SearchForFiles(FileNames); //here you add all the file names
//sort file names a la windows 7 explorer
FileNames.Sort(System.Generics.Defaults.TComparer<string>.Construct(
function (const s1, s2: string): Integer
procedure ProcessPrefix(const fn: string; var prefix, number: string);
var
I: Integer;
begin
for I := length(fn) downto 1 do
if not TCharacter.IsDigit(fn[I]) then
begin
Prefix := Copy(fn, 1, I);
number := Copy(fn, I+1, MaxInt);
Break;
end;
end;
var
prefix1, prefix2: string;
number1, number2: string;
fn1, fn2: string;
begin
//compare filenames a la windows 7 explorer
fn1 := TPath.GetFileNameWithoutExtension(s1);
fn2 := TPath.GetFileNameWithoutExtension(s2);
ProcessPrefix(fn1, prefix1, number1);
ProcessPrefix(fn2, prefix2, number2);
if (Number1 <> '') and (Number2 <> '') then
begin
Result := CompareText(prefix1, prefix2);
if Result = 0 then
Result := CompareValue(StrToInt(number1), StrToInt(Number2));
end
else
Result := CompareText(s1, s2);
end
));
UseYourSortedFileNames(FileNames);
finally
FileNames.Free;
end;
end;
By "rank", you mean sort order.
The files are sorting in the proper order (based on the ASCII value of the characters). 2 comes after 19 because the comparison is only made up to the same number of characters in both names, and '2' comes after 1.
If you want them to sort properly as numbers, you need to left-pad the numbers with zeros so they're all the same width (eg., instead of SampleFile.2.png, use SampleFile.02.png). This will cause '02' to come before 19 so they sort correctly numerically.
You can fix the numbering issue by using something like:
PngFileName := Format('SampleFile.%.2d.png', [Counter]);
I have a huge list of users and every user has it's id , but it id numbers are messed up so if anyone can show me how can I sort users by numbers , every value has this form
1:Stackoverflow
or
145000:Google
If I do that manually I think I will lose my mind since tehere are more than 700000 records.Thanks for your time and help....
Extract the number like this:
function ID(const str: string): Integer;
var
p: Integer;
begin
p := Pos(':', str);
if p=0 then
raise Exception.CreateFmt('Invalid string format: %s', [str]);
Result := StrToInt(Copy(str, 1, p-1));
end;
Once you can extract the ID as an integer you can then write a compare function. Like this:
function CompareIDs(List: TStringList; Index1, Index2: Integer): Integer;
begin
Result := CompareValue(
ID(List[Index1]),
ID(List[Index2])
);
end;
CompareValue is an RTL function that returns -1, 0 or 1 depending on the relative values of the two operands.
Feed these building blocks into TStringList.CustomSort and your job is done.
MyStringList.CustomSort(CompareIDs);
I want to create a function that receive multiples strings as parameters.
Like the function printf("Hello %s",name); of C. but I don't want to pass a ready array, it wouldn't be readable.
Edit1.text:=lang('Hello');
Edit2.text:=lang('Welcome to {1} guest',place);
Edit3.text:=lang('Hi {1}, is your {2} time in {3}','Victor','first','Disney');
output should be:
Hello
Welcome to Disney guest
Hi Victor is your first time in Disney
how I create the function TForm1.lang(parameters:String):String;, I did a research, but I can't get it work.
I need to access the parameters[] and the parameters.length also.
I'm needing this to turn my App to multilang.
Here's an example function of how you can do this:
function TForm1.lang(s: String; params: array of String): String;
var
i: Integer;
begin
for i := 0 to High(params) do
begin
ShowMessage(params[i]);
end;
end;
Call it like this:
lang('My format string', ['this', 'that']);
or like this:
var
b: String;
begin
b := 'this';
lang('My format string', [b, 'that']);
end;
Not sure what you mean by not readable
DoSomething(['Param1','Param2']);
for
procedure DoSomething(args : Array of String);
Var
Index : Integer;
Begin
for index := Low(args) to High(args) Do
ShowMessage(args[Index]);
End;
Seems okay to me. Course if you want to call it from outside delphi then you have an issue.
Quick fix is just to pass in a delimited string and then user TStringList to split it.
You could write a wee function to do that, don't forget to free it when you are done.
All your three examples could be fixed by using SysUtils.Format:
Edit1.text := format('%s',['Hello']));
Edit1.text := format('Welcome to %s guest',[place]));
Edit1.text := format('Hi %s, is your %s time in %s',['Victor','first','Disney']));
Personally I think it's quite readable. If you can have what you need from a basic sysutils function, you should seriously consider doing that, rather than to write your own version. On the other hand, you may need more complex functionality that doesn't show in your question. If that's the case, I think paulsm4's suggestion of using a stringlist seems like a good way to go.
Delphi does not support CREATING functions withvararg-style parameters that work exactly like printf() does. It only supports CONSUMING such functions from external libraries. The closest Delphi comes to supporting the creation of functions with variable parameter lists is to use "open array" parameters, like what SysUtils.Format() uses.
As Tony mentions above, I also recommend using a deliminated string. Except, a little more than just deliminating, but using more of a parsing technique. If I understand right, this function you're making for formatting shall NOT include an array in the parameters, but technically, that doesn't mean we can't use arrays anywhere at all (arrays are very ideal to use for this scenario for fast performance).
This method will allow virtually anything to be passed in the parameters, including the deliminator, without affecting the output. The idea is to do A) Size of parameter string, B) Deliminator between size and parameter, and C) parameter string... And repeat...
const
MY_DELIM = '|'; //Define a deliminator
type
TStringArray = array of String;
/////////////////////////////////
//Convert an array of string to a single parsable string
// (Will be the first step before calling your format function)
function MakeParams(const Params: array of String): String;
var
X: Integer;
S: String;
begin
Result:= '';
for X:= 0 to Length(Params)-1 do begin
S:= Params[X];
Result:= Result + IntToStr(Length(S)) + MY_DELIM + S;
end;
end;
//Convert a single parsable string to an array of string
// (Will be called inside your format function to decode)
// This is more or less called parsing
function ExtractParams(const Params: String): TStringArray;
var
S: String; //Used for temporary parsing
T: String; //Used for copying temporary data from string
P: Integer; //Used for finding positions
C: Integer; //Used for keeping track of param count
Z: Integer; //Used for keeping track of parameter sizes
begin
S:= Params; //Because we'll be using 'Delete' command
C:= 0; //Set count to 0 to start
SetLength(Result, 0); //Prepare result array to 0 parameters
while Length(S) > 0 do begin //Do loop until nothing's left
P:= Pos(MY_DELIM, S); //Get position of next deliminator
if P > 1 then begin //If deliminator was found...
C:= C + 1; //We have a new parameter
SetLength(Result, C); //Set array length to new parameter count
T:= Copy(S, 1, P-1); //Get all text up to where deliminator was found
Delete(S, 1, P); //Delete what we just copied, including deliminator
Z:= StrToIntDef(T, 0); //Convert T:String to Z: Integer for size of parameter
T:= Copy(S, 1, Z); //Get all text up to 'Z' (size of parameter)
Delete(S, 1, Z); //Delete what we just copied
Result[C-1]:= T; //Assign the new parameter to end of array result
end else begin //If deliminator was NOT found...
S:= ''; //Clear S to exit loop (possible bad format if this happens)
end;
end;
end;
//Main formatting routine
function MyFormat(const Input: String; const Params: String): String;
var
A: TStringArray;
X: Integer;
S: String;
P: Integer;
R: String;
begin
R:= Input;
A:= ExtractParams(Params);
//At this point, A contains all the parameters parsed from 'Params'
for X:= 0 to Length(A)-1 do begin
S:= A[X];
P:= Pos('%s', R);
if P > 0 then begin
Delete(R, P, 2);
Insert(S, R, P);
end;
end;
Result:= R;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
Pars: String;
begin
Pars:= MakeParams(['this', 'that', 'something else']);
Edit1.Text:= MyFormat('%s is %s but not %s', Pars);
end;
As you probably know, SysUtils.Format() implements "varargs" by using a set.
In your case, however, why not just pass a TStringList? The function will simply check "list.Count". Voila - you're done!
I have a submenu that list departments. Behind this each department have an action who's name is assigned 'actPlan' + department.name.
Now I realize this was a bad idea because the name can contain any strange character in the world but the action.name cannot contain international characters. Obviously Delphi IDE itself call some method to validate if a string is a valid componentname. Anyone know more about this ?
I have also an idea to use
Action.name := 'actPlan' + department.departmentID;
instead. The advantage is that departmentID is a known format, 'xxxxx-x' (where x is 1-9), so I have only to replace '-' with for example underscore. The problem here is that those old actionnames are already persisted in a personal textfile. It will be exceptions if I suddenly change from using departments name to the ID.
I could of course eat the exception first time and then call a method that search replace that textfile with the right data and reload it.
So basically I search the most elegant and futureproof method to solve this :)
I use D2007.
Component names are validated using the IsValidIdent function from SysUtils, which simply checks whether the first character is alphabetic or an underscore and whether all subsequent characters are alphanumeric or an underscore.
To create a string that fits those rules, simply remove any characters that don't qualify, and then add a qualifying character if the result starts with a number.
That transformation might yield the same result for similar names. If that's not something you want, then you can add something unique to the end of the string, such as a checksum computed from the input string, or your department ID.
function MakeValidIdent(const s: string): string;
var
len: Integer;
x: Integer;
c: Char;
begin
SetLength(Result, Length(s));
x := 0;
for c in s do
if c in ['A'..'Z', 'a'..'z', '0'..'9', '_'] then begin
Inc(x);
Result[x] := c;
end;
SetLength(Result, x);
if x = 0 then
Result := '_'
else if Result[1] in ['0'..'9'] then
Result := '_' + Result;
// Optional uniqueness protection follows. Choose one.
Result := Result + IntToStr(Checksum(s));
Result := Result + GetDepartment(s).ID;
end;
In Delphi 2009 and later, replace the second two in operators with calls to the CharInSet function. (Unicode characters don't work well with Delphi sets.) In Delphi 8 and earlier, change the first in operator to a classic for loop and index into s.
I have written a routine
// See SysUtils.IsValidIdent:
function MakeValidIdent(const AText: string): string;
const
Alpha = ['A'..'Z', 'a'..'z', '_'];
AlphaNumeric = Alpha + ['0'..'9'];
function IsValidChar(AIndex: Integer; AChar: Char): Boolean;
begin
if AIndex = 1 then
Result := AChar in Alpha
else
Result := AChar in AlphaNumeric;
end;
var
i: Integer;
begin
Result := AText;
for i := 1 to Length(Result) do
if not IsValidChar(i, Result[i]) then
Result[i] := '_';
end;
which makes Pascal identifiers from strings.
You might also want to copy FindUniqueName from Classes.pas and apply that to the result from MakeValidIdent.
Here is my routine:
function MakeValidIdent(const s: string): string;
begin
Result := 'clm'; //Prefix
for var c in s do
if CharInSet(c, ['A'..'Z', 'a'..'z', '0'..'9', '_']) then
Result := Result + c;
end;