Ole requiere some modification. The 0 (zero) date in Visual Fox, VB and VBA compatible products is 12/30/1899. The vbNull date es 12/31/1899. vbNull is 1 !!!!
Walter Negro El 14/11/2011 04:15 p.m., Ron Pinkas escribió: > > Hi Przemek, > > Many thanks for the detailed reply. > > Since it appears that the 2 most important differences you described > have now been addresed, I vote for complete synch, and would greatly > appreciate your help in achieving a full synch with Harbour's TIESTAMP > support. > > Please let us know which code if any will require addtional work. > > Walter, Andi, ..., any input? > > Ron > > On Nov 11, 2011 8:00 PM, "Przemysław Czerpak" <dru...@poczta.onet.pl > <mailto:dru...@poczta.onet.pl>> wrote: > > On Thu, 10 Nov 2011, Ron Pinkas wrote: > > Hi Ron, > > > Could you please help us review and consider synch issues of > > DATETIME support between Harboiur and xHarbour? > > There were some deeper modifications in this are in xHarbour > recently. I'll look at it. Initial datetime implementation in > xHarbour was really interesting and good peace of code but it > introduce some incompatibilities to Clipper and needed some > minor code cleanup. Anyhow it was not precisely defined how > it should work. Now it's the most important problem in keeping > this code alive. It's hard to cleanup anomalies when programmer > does not know expected behavior. If you agree then I can add > support for Harbour like datetime arithmetics to HVM code and > update some vital part of core code. Anyhow it's not fully > compastible with current xHarbour behavior. There were two most > importatn differences betwen Harbour and xHarbour: > 1. initial date value which can be seen in this code: > proc main() > set date format to "yyyy/mm/dd" > ? {^ 02:00 } > return > > Harbour shows: > / / 02:00:00.000 > xHarbour: > 1899/12/30 02:00:00.000 > This difference is important in code exchanging data with OLE > servers so OLE interface has to be updated to keep it. > > 2. Separate type for date values when non integer number is > aded to date item. > As I can see current xHarbour SVN works like Harbour so this > difference does not longer exists but I'm not sure if other > code which needed such behavior had been updated. > > I can add Harbour like TIMESTAMP values and update most important > parts of core non HVM code but I'm afraid I cannot make it for whole > xHarbour code. I hope that other developers can adopt their code if > necessary. As I can see in some places there is also code borrowed > from Harbour which will begin to work correctly when I'll update HVM > anyhow I cannot promise that I'll update whole xHarbour code to fully > respect new timestamp values. > Below I'm attaching small text I created to describe differences > between Harbour and xHarbour. Recent modifications in xHarbour HVM > changed xHarbour behavior so now it does not well describes it. > Anyhow it's still good description of TIMESTAMP values in Harbour > If you can accept it then I'll commit modification which introduce > it to xHarbour. > > best regards, > Przemek > > > > > ### DATETIME/TIMESTAMP VALUES ### > ======================================= > Both compilers support DATETIME/TIMESTAMP values though they use > different > implementation. > > In Harbour it's new type TIMESTAMP for which VALTYPE() function > returns > "T". It has its own HVM arithmetic similar to the one used by DATE > type > but not exactly the same. The difference (-) between two TIMESTAMP > values > is represented as number where integer part is number of days and > fractional > part is time in given day. Non-exact comparison (=, >, <, >=, <=) for > TIMESTAMP and DATA value assumes that both values are equal if the > date > part is the same. Such semantic is also respected by native RDDs when > mixed DATE and TIMESTAMP values are used in indexes, seeks, > scopes, etc. > When number is added to DATE type then like in Clipper only > integer part > increase (decrease) DATE value but when it's added to TIMESTAMP > value then > fractional part is also significant. When TIMESTAMP value is added > to DATE > value then as result new TIMESTAMP value is calculated. Here is detail > information about relational and arithmetic operators in Harbour. > Timestamp values in relational operators <, <=, >, >=, =, == > - When two timestamp values are compared then VM compares > date and > time parts in both values. > - When date and timestamp values are used in <, <=, >, >=, = > operations then VM compares only date part in both values. > - When date and timestamp values are used in == operation then VM > compares date part in both values and then check if time part > of timestamp value is 0. > Timestamp values in + and - math operations: > <t> + <t> => <t> > <t> - <t> => <n> > <t> + <n> => <t> > <n> + <t> => <t> > <t> - <n> => <t> > <d> + <t> => <t> > <t> + <d> => <t> > <d> - <t> => <n> > <t> - <d> => <n> > when number is result or argument of timestamp operation then > its integer > part is a number of days and fractional part represents time in day. > > In xHarbour DATE type was extended to hold information about time. > Clipper > compatible DATE arithmetic in HVM was modified to respect > fractional part > in numbers which was used for time part. > The xHarbour DATETIME implementation introduces incompatibilities > to Clipper > (f.e. compare Clipper and xHarbour results in code like: '? date() > + 1.125' > so in some cases existing Clipper code has to be carefully adopted > to work > correctly with xHarbour but it's fully functional solution though > it needs > some minor fixes in conversions between datetime values and numbers. > > The difference between Harbour and xHarbour can be seen in this code: > proc main() > local dVal, tVal > dVal := date() > tVal := dVal + {^ 02:00 } // {^ 02:00 } timestamp > // constant, see below > ? valtype(dVal), valtype(tVal) > ? dVal; ? tVal > dVal += 1.125 // In Clipper and Harbour it increases > // date value by 1 > tVal += 1.25 // it it increases timestamp value by 1 day > // and 6 hours > ? dVal; ? tVal > ? dVal = tVal // In Harbour .T. because date part is the same > ? date() + 0.25, date() + 0.001 == date() > return > Harbour shows: > D T > 05/20/09 > 05/20/09 02:00:00.000 > 05/21/09 > 05/21/09 08:00:00.000 > .T. > 05/20/09 .T. > > and xHarbour shows: > D D > 05/20/09 > 06/25/21 02:00:00.00 > 05/21/09 03:00:00.00 > 06/26/21 08:00:00.00 > .F. > 05/20/09 06:00:00.00 .F. > > Recently to xHarbour "T" type was introduced with some of Harbour > TIMESTAMP > code in RDD but VM was not modified to follow Harbour/RDD > modifications. > So now some parts of xHarbour are not synced and I cannot say what > is the > goal of DATETIME values and their arithmetic in xHarbour VM for > the future. > > > > ### LITERAL DATE AND TIMESTAMP VALUES ### > =============================================== > Both compilers tries to support VFP like datetime constant values > in the following format: > { ^ [ YYYY-MM-DD [,] ] [ HH[:MM[:SS][.FFF]] [AM|PM] ] } > In Harbour and VFP the following characters can be used as date > delimiters: > "-", "/" and "." > xHarbour supports only "/" as date delimiter. > There is no limit on number of digits in YYYY, MM, DD, HH, MM, SS, FFF > parts. Important is only their value. This is the format in semi > PP notation: > { ^ <YEAR> <sep:/-> <MONTH> <sep:/-> <DAY> [[<sep2:,>] > [ <HOUR> [ : <MIN> [ : <SEC> [ . <FRAQ> ] ] ] [AM|PP] ] } > NOTE: there is one important difference between Harbour and > VFP/xHarbour in > decoding above format. In VFP and xHarbour when date part is > missed then > it's set by default to: 1899-12-30 so this code: > { ^ 12:00 } > gives the same results as: > { ^ 1899/12/30 12:00 } > Harbour does not set any default date value when timestamp > constant contains > only time part. > Harbour supports VFP syntax only in Compiler. It's not supported in > macrocompiler and it can be disabled in the future so it's not > suggested > to use with Harbour programs. > > Only Harbour supports date constant (in compiler and > macrocompiler) in the > form d"YYYY-MM-DD" f.e.: > d"2009-05-20" > Also delimiter "/" or "." can be used instead of "-". > > Only Harbour supports timestamp constant (in compiler and > macrocompiler) > in the form t"YYYY-MM-DD HH:MM:SS.fff" > The exact accepted timestamp pattern is is: > YYYY-MM-DD [H[H][:M[M][:S[S][.f[f[f[f]]]]]]] [PM|AM] > f.e.: > tValue := t"2009-03-21 5:31:45.437 PM" > or: > YYYY-MM-DDT[H[H][:M[M][:S[S][.f[f[f[f]]]]]]] [PM|AM] > with literal "T" as date and time part delimiters (XML timestamp > format), > f.e.: > tValue := t"2009-03-21T17:31:45.437" > The following characters can be used as date delimiters: "-", "/", "." > if PM or AM is used HH is in range < 1 : 12 > otherwise in range < > 0 : 23 > > > Harbour compiler and macrocompiler support also date constants in the > form 0dYYYYMMDD f.e.: > 0d20090520. > > > ------------------------------------------------------------------------------ > RSA(R) Conference 2012 > Save $700 by Nov 18 > Register now > http://p.sf.net/sfu/rsa-sfdev2dev1 > > > _______________________________________________ > xHarbour-developers mailing list > xHarbour-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xharbour-developers ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ xHarbour-developers mailing list xHarbour-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xharbour-developers
