Hey guys,
Wondering if there was already a unit available that could tell me the day of week a certain date was. An example perhaps would be:

function GetDayOfWeek(date:datetimerecord):integer;

where result would be 1-7 (depending on the date).

If not, then I will just write my own, but why reinvent the wheel, eh?

- Matt

[ Charset ISO-8859-1 unsupported, converting... ]

I can't remember the exact name, but some function like that is in sysutils.

Check the documentation for more details.

Wondering if there was already a unit available that could tell me the day of week a certain date was. An example perhaps would be:

Try passing this function a packed longint and it should return the weekday in a 0..6 sequence, with 0 being Sunday. Note I didn't compile this so it might need to be tweaked. :-)

Jim

Function DayOfWeek (DateToCheck : longint) : byte
const
  FileDays : array[1..12] of byte = (6,2,2,5,0,3,5,1,4,6,2,4);
var
  DateAndTime : datetime;
  AdjustedYear : integer;
begin
  unpacktime (DateToCheck,DateAndTime);
  //  leap year adjustment
  if DateAndTime.month > 2 then AdjustedYear := DateAndTime.year else
AdjustedYear := pred (DateAndTime.year);
  WeekDay := ((DateAndTime.day + (AdjustedYear div 4) - (AdjustedYear div
100) + (AdjustedYear div 400) + DateAndTime.year + FileDays
[DateAndTime.month]) mod 7);
end;

The sysutils unit contains a function

  function DayOfWeek(DateTime: TDateTime): integer;

You'll need to convert your date to TDateTime format, though. The sysutils unit contains routines for this as well.

Michael.

At 8/30/01 01:46 PM, you wrote:

Matt,

Wondering if there was already a unit available that could tell me the day of week a certain date was. An example perhaps would be:

There is one such function in the SysUtils unit already but here you have the implementation of the original and famous Zeller closed-formula algorithm (Zeller was a mathematician way before the computer era). The wonderful part is that it doesn't need a table to know the length of the individual months but uses a multiplication and a division to calculate it... It returns 0 for Saturday, 1 for Sunday, 2 for Monday, etc. The formula is universal, it works across all centuries.

function Date2DOW (Y, D, M : cardinal) : cardinal;
var
   Century : cardinal;
begin
   Century := Y div 100;
   Y := Y mod 100;
   if M < 3 then
     begin dec (Y); inc (M, 12); end;
   Date2DOW := (((M + 1) * 26 div 10) + D + Y + (Y div 4) + (Century div 4)
- 2 * Century) mod 7;
end;

Bye,
Gábor

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G'day all..

Using fpc in OBJPAS mode I manipulate variables like this..

Type
	TTheRec = Record
	A : String[80];
	B : Cardinal;
	End;
	PTheRec = ^TTheRec;
Var
	DynArray : PTheRec;
Begin
GetMem(DynArray,SizeOf(TTheRec)*30);
DynArray[1].A := 'Hello';
DynArray[2].B := 42;
FreeMem(DynArray,SizeOf(TTheRec)*30);
End;

Under Mode Delphi, I have to do this..

Type
	TTheRec = Record
	A : String[80];
	B : Cardinal;
	End;
	PTheRec = Array [1..(MaxInt Div SizeOf(TTheRec))-1] of TTheRec;
Var
	DynArray : ^PTheRec;
Begin
GetMem(DynArray,SizeOf(TTheRec)*30);
DynArray[1].A := 'Hello';
DynArray[2].B := 42;
FreeMem(DynArray,SizeOf(TTheRec)*30);
End;

Is this the best way ?

It depends. If you're using the 1.1 compiler, the best way is to use dynamic arrays:

Type
 TheRec = Record
   A : String[80];
   B : Cardinal;
 End;
Var
  DynArray :  array of TTheRec; // No length specified
Begin
  SetLength(DynArray,30);
  DynArray[1].A := 'Hello';
  DynArray[2].B := 42;
End; // Compiler disposes of dynarray by itself.

For version 1.0 I would use the objfpc way, as it resembles more the dynamic array method.

Michael.

Problem being, it will not let me use the objfpc way with mode delphi.. I use that where I can, but some of my software needs delphi mode set, though I can't remember why for the moment..