Recent

Author Topic: problem with leap year to count.  (Read 5371 times)

mikex

  • New member
  • *
  • Posts: 7
problem with leap year to count.
« on: November 21, 2014, 11:58:15 pm »
Hi there


I have written program for school work 2 times but i cant figure out the problem. First time my program didn't counted dates like 1.1.2005 - 1.1.2007

Then I fixed that by deleting  small part and rewriting it but now it dont count the leap year .. i need it exactly from calendar .. 2012 .. 2016.. but its impossible task for me now. I have no time left to try it and fail gain. 

Commentery and counters are in my language but it does not rly matter ... ;)

Any kind of help with that would be lovely. Thanks.
var d1,d2,m1,m2,r1,r2,i,x,r1i,r2i: integer;     mesic31, mesic30: set of byte;     dni,dni2: longint;     v:array[1..12] of integer;   begin write('den1='); readln(d1); write('mesic1=');readln(m1); write('rok1=');readln(r1); write('den2=');readln(d2); write('mesic2=');readln(m2); write('rok2=');readln(r2); mesic31:=[1,3,5,7,8,10,12]; {mesice ktere maji 31 dni} mesic30:=[4,6,9,11];          {mesice ktere maji 30 dni}   r1i:=r1;r2i:=r2;       for i:=1 to 12 do begin     if i in mesic31 then     v:=31;     if i in mesic30 then     v:=30;     if i=2 then      {unor ma 28 dni}     v:=28; end;                     {rozdelime program do dvou casti: dni a dni2 , dni v rozmezi jednoho roku nebo vice let} dni:=0; for i:=m1 to 12 do         dni:=dni+v;         dni:=dni-d1; for i:=m2-1 downto 1 do         dni:=dni+v;         dni:=dni+d2; r2:=r2-1;   x:=(r2-r1) div 4;               {jednou za 4 roky pridame jeden den prestupniho roku} dni:=dni+(365*(r2-r1))+x;   dni2:=0;   for i:=m1 to m2-1 do          dni2:=dni2+v;          dni2:=dni2-d1+d2; if r1i=r2i then writeln('pocet dni je ',dni2) else writeln('pocet dni je ',dni);   readln; end.

engkin

  • Hero Member
  • *****
  • Posts: 2513
Re: problem with leap year to count.
« Reply #1 on: November 22, 2014, 02:14:58 am »
Number of days in the 2nd month of any year is a function to the year itself. It seems to me that your code assumes a fixed number: 28 days.
Code: [Select]
  for i := 1 to 12 do
  begin
..
    if i = 2 then {unor ma 28 dni}
      v[i] := 28; //<------
  end;

When you use it later in this part:
Code: [Select]
  for i := m1 to 12 do
    dni := dni + v[i];
You should consider r1.

While for next part:
Code: [Select]
  for i := m2 - 1 downto 1 do
    dni := dni + v[i];
You should consider r2.

This calculation is an approximation, but is not correct for your purpose.
Code: [Select]
  x := (r2 - r1) div 4; {jednou za 4 roky pridame jeden den prestupniho roku}
  dni := dni + (365 * (r2 - r1)) + x;
For instance, when r1 is a leap year consider the effect of having d1, m1 prior to the leap day of that year vis. after that day. On the other hand, not every four years include a leap year.

Windsurfer

  • Sr. Member
  • ****
  • Posts: 364
    • Windsurfer
Re: problem with leap year to count.
« Reply #2 on: November 22, 2014, 10:15:37 am »
I have not read your code, but a year is a leap year if it is divisible by 4 unless it is divisible by 100 unless it is divisible by 1000.

Note the second 'unless'. This means that all years divisible by 1000 are NOT leap years. This is a common mistake.

engkin

  • Hero Member
  • *****
  • Posts: 2513
Re: problem with leap year to count.
« Reply #3 on: November 22, 2014, 10:42:11 am »
I have not read your code, but a year is a leap year if it is divisible by 4 unless it is divisible by 100 unless it is divisible by 1000.

Note the second 'unless'. This means that all years divisible by 1000 are NOT leap years. This is a common mistake.
It is 400, not 1000. I know you won't take my word for it  :P, so here is Wikipedia:
Quote
if (year is not divisible by 4) then (it is a common year)
else
if (year is not divisible by 100) then (it is a leap year)
else
if (year is not divisible by 400) then (it is a common year)
else (it is a leap year)

marcov

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8803
  • FPC developer.
Re: problem with leap year to count.
« Reply #4 on: November 22, 2014, 05:58:19 pm »
Dateutils has

Code: [Select]
Function IsInLeapYear(const AValue: TDateTime): Boolean;

engkin

  • Hero Member
  • *****
  • Posts: 2513
Re: problem with leap year to count.
« Reply #5 on: November 22, 2014, 07:45:12 pm »
Dateutils has

Code: [Select]
Function IsInLeapYear(const AValue: TDateTime): Boolean;
Can't be used in school assignment.

Bart

  • Hero Member
  • *****
  • Posts: 3955
    • Bart en Mariska's Webstek
Re: problem with leap year to count.
« Reply #6 on: November 22, 2014, 11:13:09 pm »
Dateutils has

Code: [Select]
Function IsInLeapYear(const AValue: TDateTime): Boolean;
Can't be used in school assignment.

But function can be copied to impress teacher.

Bart

BrunoK

  • Sr. Member
  • ****
  • Posts: 267
  • Retired programmer
Re: problem with leap year to count.
« Reply #7 on: November 23, 2014, 12:05:51 pm »
Or a different one.
Code: [Select]
  function Fun_IsLeapYear(aYear: integer): boolean;
begin
  Result := (aYear and 3) = 0;   // Test simple case
  if Result then begin
    aYear:=aYear shr 2;          // Reduce (Divide by 4)
    Result:=(aYear mod 25)<>0;   // Eliminate those that cannot
    if not Result then           // ..be divided by 100, they are always leaps
      Result:=(aYear and 3)=0;   // Those that can be divided by 4(00) are leaps
  end;
end;

Windsurfer

  • Sr. Member
  • ****
  • Posts: 364
    • Windsurfer
Re: problem with leap year to count.
« Reply #8 on: November 23, 2014, 05:42:22 pm »
Engkin,  thanks for the correction.  Thankfully I did know it correctly in 1999!
The lesson for me is to check before posting.

engkin

  • Hero Member
  • *****
  • Posts: 2513
Re: problem with leap year to count.
« Reply #9 on: November 24, 2014, 12:09:33 am »
But function can be copied to impress teacher.
@Bart, your reply cheered me up, thanks. Impressing teachers would result in harder assignments!

Thankfully I did know it correctly in 1999!
@Windsurfer, retaining anything related to this for so long is nearly impossible for me.

 

TinyPortal © 2005-2018