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[Rcpp-devel] Datetime substraction bug ?

8 messages · Robin Girard, Dirk Eddelbuettel, stat quant

Original
Robin Girard
# 
Hi List

why is it that we have in the Datetime definition
(here http://dirk.eddelbuettel.com/code/rcpp/html/Date_8cpp_source.html#l00271 )

double operator-(const Datetime& d1, const Datetime& d2) { return d2.m_dt - d1.m_dt; }
bool operator<(const Datetime &d1, const Datetime& d2) { return d1.m_dt < d2.m_dt; }

I feel there is a contradiction 
substraction shoulb be d1.m_dt - d2.m_dt;  no ? 

Robin

Dr. Girard Robin
Charg? de Recherche

MINES-ParisTech / D?partement Energ?tique et Proc?d?s / PERSEE / Groupe ERSEI
Centre Proc?d?s, Energies Renouvelables et Syst?mes Energ?tiques (PERSEE)
Center for Processes, Renewables Energies and Energy Systems
Renewable Energies & Smartgrids (ERSEI)

1 Rue Claude Daunesse - CS 10207 - F-06904 Sophia Antipolis Cedex
Tel: +33.4.93.67.89.64 (~99), Fax: +33.4.93.95.75.35
e-mail : robin.girard at mines-paristech.fr

web page perso http://www.mines-paristech.fr/Services/Annuaire/&?id=8828
statoverflow : http://stats.stackexchange.com/users/223/robin-girard
web page centre PERSEE : http://www.cep.mines-paristech.fr/
linkedin : http://www.linkedin.com/profile/view?id=14907272&trk=tab_pro

Le lien vaut mieux que le bien.
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Dirk Eddelbuettel
#
On 29 March 2013 at 23:37, Robin Girard wrote:
| Hi List
| 
| why is it that we have in the Datetime definition
| (here http://dirk.eddelbuettel.com/code/rcpp/html/Date_8cpp_source.html#l00271 )
| 
| double operator-(const Datetime& d1, const Datetime& d2) { return d2.m_dt - d1.m_dt; }
| bool operator<(const Datetime &d1, const Datetime& d2) { return d1.m_dt < d2.m_dt; }
| 
| I feel there is a contradiction 
| substraction shoulb be d1.m_dt - d2.m_dt;  no ? 

It's been a while since I wrote that and I think I followed the difftime()
convention in R. Or maybe not.  To me d1 comes before d2 in the way the
arguments are given, so d2 is larger and I want to subtract d1 from d2.

In any event, if it bugs you greatly you are always free to write your own
function. ;-)

Dirk

| 
| Robin
| 
| Dr. Girard Robin
| Charg? de Recherche
| 
| MINES-ParisTech / D?partement Energ?tique et Proc?d?s / PERSEE / Groupe ERSEI
| Centre Proc?d?s, Energies Renouvelables et Syst?mes Energ?tiques (PERSEE)
| Center for Processes, Renewables Energies and Energy Systems
| Renewable Energies & Smartgrids (ERSEI)
| 
| 1 Rue Claude Daunesse - CS 10207 - F-06904 Sophia Antipolis Cedex
| Tel: +33.4.93.67.89.64 (~99), Fax: +33.4.93.95.75.35
| e-mail : robin.girard at mines-paristech.fr
| 
| web page perso http://www.mines-paristech.fr/Services/Annuaire/&?id=8828
| statoverflow : http://stats.stackexchange.com/users/223/robin-girard
| web page centre PERSEE : http://www.cep.mines-paristech.fr/
| linkedin : http://www.linkedin.com/profile/view?id=14907272&trk=tab_pro
| 
| Le lien vaut mieux que le bien.
| ________________________________________________________
| 
| CONFIDENTIALITY : This  e-mail  and  any attachments are
| confidential and may be privileged. If  you are not a
| named recipient, please notify the sender immediately and
| do not disclose the contents to another person, use it for
| any purpose or store or copy the information in any medium.
| 
| CONFIDENTIALITE : Ce message et les ?ventuelles pi?ces
| attach?es sontconfidentiels et peuvent ?tre une
| communication prot?g?e. Si vous n'?tes pas dans la liste
| des destinataires, veuillez informer l'exp?diteur
| imm?diatement et ne pas ouvrir ni divulguer le contenu
| ? une tierce personne, ne pas l'utiliser pour quelque
| raison que ce soit, ne pas stocker ou copier l'information
| qu'il contient sur un quelconque support.
| 
| _______________________________________________
| Rcpp-devel mailing list
| Rcpp-devel at lists.r-forge.r-project.org
| https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
Robin Girard
# 
Thanks you're right  I already wrote it myself with getFractional...
and indeed that's not really what we should call a "bug" but it took me a while to understand that 

if date1-date2>0  then date1<date2 ;)

R.


----- Mail original -----
De: "Dirk Eddelbuettel" <edd at debian.org>
?: "Robin Girard" <robin.girard at mines-paristech.fr>
Cc: rcpp-devel at lists.r-forge.r-project.org
Envoy?: Samedi 30 Mars 2013 00:44:08
Objet: Re: [Rcpp-devel] Datetime substraction bug ?
On 29 March 2013 at 23:37, Robin Girard wrote:
| Hi List
| 
| why is it that we have in the Datetime definition
| (here http://dirk.eddelbuettel.com/code/rcpp/html/Date_8cpp_source.html#l00271 )
| 
| double operator-(const Datetime& d1, const Datetime& d2) { return d2.m_dt - d1.m_dt; }
| bool operator<(const Datetime &d1, const Datetime& d2) { return d1.m_dt < d2.m_dt; }
| 
| I feel there is a contradiction 
| substraction shoulb be d1.m_dt - d2.m_dt;  no ? 

It's been a while since I wrote that and I think I followed the difftime()
convention in R. Or maybe not.  To me d1 comes before d2 in the way the
arguments are given, so d2 is larger and I want to subtract d1 from d2.

In any event, if it bugs you greatly you are always free to write your own
function. ;-)

Dirk

| 
| Robin
| 
| Dr. Girard Robin
| Charg? de Recherche
| 
| MINES-ParisTech / D?partement Energ?tique et Proc?d?s / PERSEE / Groupe ERSEI
| Centre Proc?d?s, Energies Renouvelables et Syst?mes Energ?tiques (PERSEE)
| Center for Processes, Renewables Energies and Energy Systems
| Renewable Energies & Smartgrids (ERSEI)
| 
| 1 Rue Claude Daunesse - CS 10207 - F-06904 Sophia Antipolis Cedex
| Tel: +33.4.93.67.89.64 (~99), Fax: +33.4.93.95.75.35
| e-mail : robin.girard at mines-paristech.fr
| 
| web page perso http://www.mines-paristech.fr/Services/Annuaire/&?id=8828
| statoverflow : http://stats.stackexchange.com/users/223/robin-girard
| web page centre PERSEE : http://www.cep.mines-paristech.fr/
| linkedin : http://www.linkedin.com/profile/view?id=14907272&trk=tab_pro
| 
| Le lien vaut mieux que le bien.
| ________________________________________________________
| 
| CONFIDENTIALITY : This  e-mail  and  any attachments are
| confidential and may be privileged. If  you are not a
| named recipient, please notify the sender immediately and
| do not disclose the contents to another person, use it for
| any purpose or store or copy the information in any medium.
| 
| CONFIDENTIALITE : Ce message et les ?ventuelles pi?ces
| attach?es sontconfidentiels et peuvent ?tre une
| communication prot?g?e. Si vous n'?tes pas dans la liste
| des destinataires, veuillez informer l'exp?diteur
| imm?diatement et ne pas ouvrir ni divulguer le contenu
| ? une tierce personne, ne pas l'utiliser pour quelque
| raison que ce soit, ne pas stocker ou copier l'information
| qu'il contient sur un quelconque support.
| 
| _______________________________________________
| Rcpp-devel mailing list
| Rcpp-devel at lists.r-forge.r-project.org
| https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
1 day later
stat quant
# 
Thanks a lot for reporting this I would surely have been caught (may be I
am I'll go through code I wrote using this) by this bug.
Posting your workaround would not hurt I think...

Thanks and cheers

2013/3/30 Robin Girard <robin.girard at mines-paristech.fr>
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Robin Girard
# 
Actually that's not a big trick 
date.getFractionalTimestamp() returns date.m_dt which is a double. The substraction on double is the "usual one" and 
date_end.getFractionalTimestamp()-date_begin.getFractionalTimestamp() gives a positive number if and only if date_end>date_begin. 
 
My only regret is that it gives longer code line and less ease of reading. But I clearly understand that it's a matter of convention and if other have integrated this convention this cannot be changed now, otherwise it will become a bug for them...

at the end a "bug" is only a missinterpretation of something somewhere ? :) 

lots of .getFractionalTimestamp() everywhere for me ... 
R.


----- Mail original -----
De: "stat quant" <statquant at outlook.com>
?: "Robin Girard" <robin.girard at mines-paristech.fr>
Cc: rcpp-devel at lists.r-forge.r-project.org
Envoy?: Dimanche 31 Mars 2013 11:32:08
Objet: Re: [Rcpp-devel] Datetime substraction bug ?

Thanks a lot for reporting this I would surely have been caught (may be I am I'll go through code I wrote using this) by this bug. 
Posting your workaround would not hurt I think... 

Thanks and cheers 


2013/3/30 Robin Girard < robin.girard at mines-paristech.fr > 


Thanks you're right I already wrote it myself with getFractional... 
and indeed that's not really what we should call a "bug" but it took me a while to understand that 

if date1-date2>0 then date1<date2 ;) 

R. 


----- Mail original ----- 
De: "Dirk Eddelbuettel" < edd at debian.org > 
?: "Robin Girard" < robin.girard at mines-paristech.fr > 
Cc: rcpp-devel at lists.r-forge.r-project.org 
Envoy?: Samedi 30 Mars 2013 00:44:08 
Objet: Re: [Rcpp-devel] Datetime substraction bug ?
On 29 March 2013 at 23:37, Robin Girard wrote:
| Hi List 
| 
| why is it that we have in the Datetime definition 
| (here http://dirk.eddelbuettel.com/code/rcpp/html/Date_8cpp_source.html#l00271 ) 
| 
| double operator-(const Datetime& d1, const Datetime& d2) { return d2.m_dt - d1.m_dt; } 
| bool operator<(const Datetime &d1, const Datetime& d2) { return d1.m_dt < d2.m_dt; } 
| 
| I feel there is a contradiction 
| substraction shoulb be d1.m_dt - d2.m_dt; no ? 

It's been a while since I wrote that and I think I followed the difftime() 
convention in R. Or maybe not. To me d1 comes before d2 in the way the 
arguments are given, so d2 is larger and I want to subtract d1 from d2. 

In any event, if it bugs you greatly you are always free to write your own 
function. ;-) 

Dirk 

| 
| Robin 
| 
| Dr. Girard Robin 
| Charg? de Recherche 
| 
| MINES-ParisTech / D?partement Energ?tique et Proc?d?s / PERSEE / Groupe ERSEI 
| Centre Proc?d?s, Energies Renouvelables et Syst?mes Energ?tiques (PERSEE) 
| Center for Processes, Renewables Energies and Energy Systems 
| Renewable Energies & Smartgrids (ERSEI) 
| 
| 1 Rue Claude Daunesse - CS 10207 - F-06904 Sophia Antipolis Cedex 
| Tel: +33.4.93.67.89.64 (~99), Fax: +33.4.93.95.75.35 
| e-mail : robin.girard at mines-paristech.fr 
| 
| web page perso http://www.mines-paristech.fr/Services/Annuaire/&?id=8828 
| statoverflow : http://stats.stackexchange.com/users/223/robin-girard 
| web page centre PERSEE : http://www.cep.mines-paristech.fr/ 
| linkedin : http://www.linkedin.com/profile/view?id=14907272&trk=tab_pro 
| 
| Le lien vaut mieux que le bien. 
| ________________________________________________________ 
| 
| CONFIDENTIALITY : This e-mail and any attachments are 
| confidential and may be privileged. If you are not a 
| named recipient, please notify the sender immediately and 
| do not disclose the contents to another person, use it for 
| any purpose or store or copy the information in any medium. 
| 
| CONFIDENTIALITE : Ce message et les ?ventuelles pi?ces 
| attach?es sontconfidentiels et peuvent ?tre une 
| communication prot?g?e. Si vous n'?tes pas dans la liste 
| des destinataires, veuillez informer l'exp?diteur 
| imm?diatement et ne pas ouvrir ni divulguer le contenu 
| ? une tierce personne, ne pas l'utiliser pour quelque 
| raison que ce soit, ne pas stocker ou copier l'information 
| qu'il contient sur un quelconque support. 
| 
| _______________________________________________ 
| Rcpp-devel mailing list 
| Rcpp-devel at lists.r-forge.r-project.org 
| https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
stat quant
# 
Thanks,
agreed, "bug" can be replaced by "feature" here, though a surprisingly
strange one as I never encountered such in any dateTime class.
Good news is that operator < is implemented as I thought

   - bool operator<<http://dirk.eddelbuettel.com/code/rcpp/html/namespaceRcpp.html#adf2a70049435b345d5d049c3ab00658b>
   (const Datetime<http://dirk.eddelbuettel.com/code/rcpp/html/classRcpp_1_1Datetime.html>&d1,
   const Datetime<http://dirk.eddelbuettel.com/code/rcpp/html/classRcpp_1_1Datetime.html>&
   d2) { return
d1.m_dt<http://dirk.eddelbuettel.com/code/rcpp/html/classRcpp_1_1Datetime.html#a0655024a342ad356a28b3a58d4886956><
d2.
   m_dt<http://dirk.eddelbuettel.com/code/rcpp/html/classRcpp_1_1Datetime.html#a0655024a342ad356a28b3a58d4886956>;
   }

It teaches a lesson: always go and check the sources (unless you are
looking at a commutative operator ;))

2013/3/31 Robin Girard <robin.girard at mines-paristech.fr>
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Dirk Eddelbuettel
# 
I don't really understand all the excitement here.  

It's quick enough to define a function to do what you want, no?

R> NewYear <- as.Date("2013-01-01")
R> Easter <- Sys.Date()
R> cppFunction('double ddiff(Date a, Date b) { return a - b; }')
R> cppFunction('double ddiff2(Date a, Date b) { return b - a; }')
R> ddiff(NewYear, Easter)
[1] 89                            ## I find this more logical
R> ddiff2(NewYear, Easter)
[1] -89                           ## closer to R's difftime and 'odd' to me
R> 

Dirk
stat quant
# 
Hello Dirk,
no excitement at all, very simple it is.
We were merely pinpointing that this definition of "operator -" was very
unintuitive, but hey, you wrote the code, your right to put it the way you
want, I am very happy to have have the right to use it for free.

Cheers

2013/3/31 Dirk Eddelbuettel <edd at debian.org>
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