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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- A D A . C A L E N D A R . A R I T H M E T I C --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2005-2017, Free Software Foundation, Inc. --
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10 -- --
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11 -- This specification is derived from the Ada Reference Manual for use with --
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12 -- GNAT. In accordance with the copyright of that document, you can freely --
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13 -- copy and modify this specification, provided that if you redistribute a --
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14 -- modified version, any changes that you have made are clearly indicated. --
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15 -- --
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16 ------------------------------------------------------------------------------
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17
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18 -- This package provides arithmetic operations of time values using days
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19 -- and leap seconds. Ada.Calendar.Arithmetic is defined in the Ada 2005
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20 -- RM (9.6.1).
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21
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22 package Ada.Calendar.Arithmetic is
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23
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24 -- Arithmetic on days:
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25
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26 -- Rough estimate on the number of days over the range of Ada time
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27
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28 type Day_Count is range
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29 -(366 * (1 + Year_Number'Last - Year_Number'First))
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30 ..
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31 +(366 * (1 + Year_Number'Last - Year_Number'First));
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32
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33 subtype Leap_Seconds_Count is Integer range -2047 .. 2047;
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34 -- Count of leap seconds. Negative leap seconds occur whenever the
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35 -- astronomical time is faster than the atomic time or as a result of
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36 -- Difference when Left < Right.
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37
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38 procedure Difference
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39 (Left : Time;
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40 Right : Time;
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41 Days : out Day_Count;
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42 Seconds : out Duration;
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43 Leap_Seconds : out Leap_Seconds_Count);
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44 -- Returns the difference between Left and Right. Days is the number of
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45 -- days of difference, Seconds is the remainder seconds of difference
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46 -- excluding leap seconds, and Leap_Seconds is the number of leap seconds.
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47 -- If Left < Right, then Seconds <= 0.0, Days <= 0, and Leap_Seconds <= 0,
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48 -- otherwise all values are nonnegative. The absolute value of Seconds is
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49 -- always less than 86_400.0. For the returned values, if Days = 0, then
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50 -- Seconds + Duration (Leap_Seconds) = Calendar."-" (Left, Right)
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51
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52 function "+" (Left : Time; Right : Day_Count) return Time;
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53 function "+" (Left : Day_Count; Right : Time) return Time;
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54 -- Adds a number of days to a time value. Time_Error is raised if the
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55 -- result is not representable as a value of type Time.
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56
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57 function "-" (Left : Time; Right : Day_Count) return Time;
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58 -- Subtracts a number of days from a time value. Time_Error is raised if
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59 -- the result is not representable as a value of type Time.
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60
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61 function "-" (Left : Time; Right : Time) return Day_Count;
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62 -- Subtracts two time values, and returns the number of days between them.
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63 -- This is the same value that Difference would return in Days.
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64
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65 end Ada.Calendar.Arithmetic;
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