g-calend.adb (Has_53_Weeks): Rename to Last_Year_Has_53_Weeks.
2007-09-26 Hristian Kirtchev <kirtchev@adacore.com> * g-calend.adb (Has_53_Weeks): Rename to Last_Year_Has_53_Weeks. Add a call to Jan_1_Day _Of_Week to optimize its performance. (Is_Leap): Move the routine to the scope of Week_In_Year. (Jan_1_Day_Of_Week): New routine in Week_In_Year which calculates the weekday on which January 1 falls of Year - 1 and Year + 1. This function avoids calling Time_Of and Split, thus making it more efficent. (Week_In_Year): Reimplemented in oder to follow ISO 8601. * g-calend.ads (Week_In_Year): Change comment to reflect new implementation. From-SVN: r128790
This commit is contained in:
Hristian Kirtchev
Arnaud Charlet
parent
31b5873d01
commit
dd05ba2754
@ -6,7 +6,7 @@
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1999-2006, AdaCore --
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-- Copyright (C) 1999-2007, AdaCore --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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@ -45,10 +45,8 @@ package body GNAT.Calendar is
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Month : Month_Number;
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Day : Day_Number;
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Day_Secs : Day_Duration;
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begin
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Split (Date, Year, Month, Day, Day_Secs);
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return Julian_Day (Year, Month, Day) - Julian_Day (Year, 1, 1) + 1;
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end Day_In_Year;
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@ -61,10 +59,8 @@ package body GNAT.Calendar is
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Month : Month_Number;
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Day : Day_Number;
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Day_Secs : Day_Duration;
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begin
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Split (Date, Year, Month, Day, Day_Secs);
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return Day_Name'Val ((Julian_Day (Year, Month, Day)) mod 7);
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end Day_Of_Week;
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@ -80,7 +76,6 @@ package body GNAT.Calendar is
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Minute : Minute_Number;
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Second : Second_Number;
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Sub_Second : Second_Duration;
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begin
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Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
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return Hour;
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@ -140,7 +135,6 @@ package body GNAT.Calendar is
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Minute : Minute_Number;
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Second : Second_Number;
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Sub_Second : Second_Duration;
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begin
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Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
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return Minute;
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@ -158,7 +152,6 @@ package body GNAT.Calendar is
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Minute : Minute_Number;
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Second : Second_Number;
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Sub_Second : Second_Duration;
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begin
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Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
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return Second;
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@ -209,7 +202,6 @@ package body GNAT.Calendar is
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Minute : Minute_Number;
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Second : Second_Number;
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Sub_Second : Second_Duration;
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begin
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Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
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return Sub_Second;
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@ -301,16 +293,246 @@ package body GNAT.Calendar is
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Minute : Minute_Number;
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Second : Second_Number;
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Sub_Second : Second_Duration;
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Offset : Natural;
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Jan_1 : Day_Name;
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Shift : Week_In_Year_Number;
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Start_Week : Week_In_Year_Number;
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function Is_Leap (Year : Year_Number) return Boolean;
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-- Return True if Year denotes a leap year. Leap centential years are
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-- properly handled.
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function Jan_1_Day_Of_Week
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(Jan_1 : Day_Name;
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Year : Year_Number;
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Last_Year : Boolean := False;
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Next_Year : Boolean := False) return Day_Name;
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-- Given the weekday of January 1 in Year, determine the weekday on
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-- which January 1 fell last year or will fall next year as set by
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-- the two flags. This routine does not call Time_Of or Split.
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function Last_Year_Has_53_Weeks
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(Jan_1 : Day_Name;
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Year : Year_Number) return Boolean;
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-- Given the weekday of January 1 in Year, determine whether last year
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-- has 53 weeks. A False value implies that the year has 52 weeks.
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-------------
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-- Is_Leap --
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-------------
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function Is_Leap (Year : Year_Number) return Boolean is
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begin
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if Year mod 400 = 0 then
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return True;
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elsif Year mod 100 = 0 then
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return False;
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else
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return Year mod 4 = 0;
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end if;
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end Is_Leap;
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-----------------------
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-- Jan_1_Day_Of_Week --
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-----------------------
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function Jan_1_Day_Of_Week
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(Jan_1 : Day_Name;
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Year : Year_Number;
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Last_Year : Boolean := False;
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Next_Year : Boolean := False) return Day_Name
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is
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Shift : Integer := 0;
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begin
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if Last_Year then
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if Is_Leap (Year - 1) then
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Shift := -2;
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else
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Shift := -1;
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end if;
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elsif Next_Year then
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if Is_Leap (Year) then
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Shift := 2;
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else
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Shift := 1;
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end if;
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end if;
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return Day_Name'Val ((Day_Name'Pos (Jan_1) + Shift) mod 7);
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end Jan_1_Day_Of_Week;
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----------------------------
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-- Last_Year_Has_53_Weeks --
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----------------------------
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function Last_Year_Has_53_Weeks
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(Jan_1 : Day_Name;
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Year : Year_Number) return Boolean
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is
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Last_Jan_1 : constant Day_Name :=
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Jan_1_Day_Of_Week (Jan_1, Year, Last_Year => True);
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begin
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-- These two cases are illustrated in the table below
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return
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Last_Jan_1 = Thursday
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or else
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(Last_Jan_1 = Wednesday
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and then Is_Leap (Year - 1));
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end Last_Year_Has_53_Weeks;
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-- Start of processing for Week_In_Year
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begin
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Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
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-- Day offset number for the first week of the year
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-- According to ISO 8601, the first week of year Y is the week that
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-- contains the first Thursday in year Y. The following table contains
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-- all possible combinations of years and weekdays along with examples.
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Offset := Julian_Day (Year, 1, 1) mod 7;
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-- +-------+------+-------+---------+
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-- | Jan 1 | Leap | Weeks | Example |
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-- +-------+------+-------+---------+
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-- | Mon | No | 52 | 2007 |
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-- +-------+------+-------+---------+
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-- | Mon | Yes | 52 | 1996 |
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-- +-------+------+-------+---------+
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-- | Tue | No | 52 | 2002 |
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-- +-------+------+-------+---------+
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-- | Tue | Yes | 52 | 1980 |
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-- +-------+------+-------+---------+
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-- | Wed | No | 52 | 2003 |
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-- +-------+------#########---------+
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-- | Wed | Yes # 53 # 1992 |
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-- +-------+------#-------#---------+
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-- | Thu | No # 53 # 1998 |
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-- +-------+------#-------#---------+
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-- | Thu | Yes # 53 # 2004 |
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-- +-------+------#########---------+
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-- | Fri | No | 52 | 1999 |
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-- +-------+------+-------+---------+
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-- | Fri | Yes | 52 | 1988 |
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-- +-------+------+-------+---------+
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-- | Sat | No | 52 | 1994 |
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-- +-------+------+-------+---------+
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-- | Sat | Yes | 52 | 1972 |
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-- +-------+------+-------+---------+
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-- | Sun | No | 52 | 1995 |
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-- +-------+------+-------+---------+
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-- | Sun | Yes | 52 | 1956 |
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-- +-------+------+-------+---------+
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return 1 + ((Day_In_Year (Date) - 1) + Offset) / 7;
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-- A small optimization, the input date is January 1. Note that this
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-- is a key day since it determines the number of weeks and is used
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-- when special casing the first week of January and the last week of
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-- December.
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if Day = 1
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and then Month = 1
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then
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Jan_1 := Day_Of_Week (Date);
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else
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Jan_1 := Day_Of_Week (Time_Of (Year, 1, 1, 0.0));
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end if;
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if Month = 1 then
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-- Special case 1: January 1, 2 and 3. These three days may belong
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-- to last year's last week which can be week number 52 or 53.
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-- +-----+-----+-----+=====+-----+-----+-----+
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-- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 26 | 27 | 28 # 29 # 30 | 31 | 1 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 27 | 28 | 29 # 30 # 31 | 1 | 2 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 28 | 29 | 30 # 31 # 1 | 2 | 3 |
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-- +-----+-----+-----+=====+-----+-----+-----+
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if (Day = 1 and then Jan_1 in Friday .. Sunday)
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or else
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(Day = 2 and then Jan_1 in Friday .. Saturday)
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or else
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(Day = 3 and then Jan_1 = Friday)
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then
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if Last_Year_Has_53_Weeks (Jan_1, Year) then
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return 53;
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else
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return 52;
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end if;
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-- Special case 2: January 1, 2, 3, 4, 5 and 6 of the first week. In
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-- this scenario January 1 does not fall on a Monday.
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-- +-----+-----+-----+=====+-----+-----+-----+
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-- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 29 | 30 | 31 # 1 # 2 | 3 | 4 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 30 | 31 | 1 # 2 # 3 | 4 | 5 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 31 | 1 | 2 # 3 # 4 | 5 | 6 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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elsif (Day <= 4 and then Jan_1 in Tuesday .. Thursday)
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or else
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(Day = 5 and then Jan_1 in Tuesday .. Wednesday)
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or else
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(Day = 6 and then Jan_1 = Tuesday)
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then
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return 1;
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end if;
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-- Special case 3: December 29, 30 and 31. These days may belong to
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-- next year's first week.
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-- +-----+-----+-----+=====+-----+-----+-----+
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-- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 29 | 30 | 31 # 1 # 2 | 3 | 4 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 30 | 31 | 1 # 2 # 3 | 4 | 5 |
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-- +-----+-----+-----+-----+-----+-----+-----+
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-- | 31 | 1 | 2 # 3 # 4 | 5 | 6 |
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-- +-----+-----+-----+=====+-----+-----+-----+
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elsif Month = 12
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and then Day > 28
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then
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declare
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Next_Jan_1 : constant Day_Name :=
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Jan_1_Day_Of_Week (Jan_1, Year, Next_Year => True);
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begin
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if (Day = 29 and then Next_Jan_1 = Thursday)
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or else
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(Day = 30 and then Next_Jan_1 in Wednesday .. Thursday)
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or else
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(Day = 31 and then Next_Jan_1 in Tuesday .. Thursday)
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then
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return 1;
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end if;
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end;
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end if;
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-- Determine the week from which to start counting. If January 1 does
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-- not belong to the first week of the input year, then the next week
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-- is the first week.
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if Jan_1 in Friday .. Sunday then
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Start_Week := 1;
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else
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Start_Week := 2;
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end if;
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-- At this point all special combinations have been accounted for and
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-- the proper start week has been found. Since January 1 may not fall
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-- on a Monday, shift 7 - Day_Name'Pos (Jan_1). This action ensures an
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-- origin which falls on Monday.
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Shift := 7 - Day_Name'Pos (Jan_1);
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return Start_Week + (Day_In_Year (Date) - Shift - 1) / 7;
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end Week_In_Year;
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end GNAT.Calendar;
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@ -6,7 +6,7 @@
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1999-2006, Free Software Foundation, Inc. --
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-- Copyright (C) 1999-2007, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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@ -72,7 +72,13 @@ package GNAT.Calendar is
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-- December is day 365 or 366 for leap year).
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function Week_In_Year (Date : Ada.Calendar.Time) return Week_In_Year_Number;
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-- Returns the week number in the year with Monday as first day of week
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-- Returns the week number as defined in ISO 8601. A week always starts on
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-- a Monday and the first week of a particular year is the one containing
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-- the first Thursday. A year may have 53 weeks when January 1st is a
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-- Wednesday and the year is leap or January 1st is a Thursday. Note that
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-- the last days of December may belong to the first week on the next year
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-- and conversely, the first days of January may belong to the last week
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-- of the last year.
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procedure Split
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(Date : Ada.Calendar.Time;
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