Change operator< from FairTimeStamp* to FairTimeStamp&

[TobiasStockmanns]

The behaviour of the FairTimeStamp::operator< does no follow standard behaviour by dealing with the FairTimeStamp* instead of a FairTimeStamp&. This is fixed in this merge request. Should fix issue #1519.

Describe your proposal.

Mention any issue this PR resolves or is related to.

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Checklist:

• [ ] Followed the Contributing Guidelines

Summary by CodeRabbit

• Refactor
  • Updated the comparison method in the timestamp functionality to enhance reliability and performance.

[coderabbitai[bot]]

Walkthrough

Walkthrough

The recent update in the FairRoot project involves modifying the operator< method in the FairTimeStamp class to use a reference instead of a pointer. This change aims to enhance the method's usability and address compatibility issues with newer compiler versions that have stricter overload rules.

Changes

File Path	Change Summary
fairroot/base/event/FairTimeStamp.h	Changed operator< from taking a pointer to taking a reference.

Possibly related issues

• FairRootGroup/FairRoot#1519: The change to operator< in FairTimeStamp might resolve the compiler warning about hidden overloaded virtual function, as the method signature now properly differentiates from similar methods in derived classes.

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Recent Review Details

Configuration used: CodeRabbit UI Review profile: CHILL

Commits

Files that changed from the base of the PR and between 5c154f07fe61d1bea877483e623580b1879d2e49 and e891df5c270be9c1a53c693dd027d9bce1b90e8d.

Files selected for processing (1)

• fairroot/base/event/FairTimeStamp.h (2 hunks)

Files skipped from review as they are similar to previous changes (1)

• fairroot/base/event/FairTimeStamp.h

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[fuhlig1]

@TobiasStockmanns,

I don't understand why the operator is needed at all. I is neither used in FairRoot nor PandaRoot which was checked by Radek and me independently. Radek simply removed the function, I add the function with =delete. In both cases we did not see any compilation errors. To cross-check I add a test which uses the operator< and this file shows the following error message during compilation

/opt/fairroot/source/v19.0/tests/base/event/test_FairTimeStamp.cxx:20:9: error: overload resolution selected deleted operator '<'
   if (a<b) { a=2.;}
       ~^~
/opt/fairroot/source/v19.0/fairroot/base/event/FairTimeStamp.h:63:11: note: candidate function has been explicitly deleted
     bool operator<(const FairTimeStamp& rValue) = delete;
          ^
/opt/fairsoft/jan24/include/root/TString.h:778:15: note: candidate function not viable: no known conversion from 'FairTimeStamp' to 'const TString' for 1st argument
inline Bool_t operator<(const TString &s1, const TString &s2)
              ^
/opt/fairsoft/jan24/include/root/TString.h:794:15: note: candidate function not viable: no known conversion from 'FairTimeStamp' to 'const TString' for 1st argument
inline Bool_t operator<(const TString &s1, const char *s2)
              ^
/opt/fairsoft/jan24/include/root/TString.h:812:15: note: candidate function not viable: no known conversion from 'FairTimeStamp' to 'const char *' for 1st argument
inline Bool_t operator<(const char *s1, const TString &s2)
              ^
/opt/fairroot/source/v19.0/fairroot/base/event/FairTimeStamp.h:64:11: note: candidate function not viable: no known conversion from 'FairTimeStamp' to 'const FairTimeStamp *' for 1st argument; take the address of the argument with &
     bool operator<(const FairTimeStamp* rValue) = delete;
          ^

I don't see the need for the overloaded function and would propose to simply delete it or at least set it as deprecated.

[TobiasStockmanns]

The original idea why I defined bool operator<(const FairTimeStamp* rValue) was to be able to sort a container of FairTimeStamp* with this operator. Unfortunately this does not work because the sort will always use the memory location and not the FairTimeStamp::operator<. So this implementation does not make any sense. Nevertheless I think it is good to have an bool operator<(const FairTimeStamp& rValue) defined, because for time based simulations and reconstructions a sorting by the time stamp is mandatory and this should be supported by the code. In addition the virtual should be removed.

[karabowi]

@coderabbitai construct short CHANGELOG message for this PR. @TobiasStockmanns , can you squash into one commit?

[coderabbitai[bot]]

[!TIP] For best results, initiate chat on the files or code changes.

@karabowi, here's a short CHANGELOG message for PR #1526:

- Updated `FairTimeStamp::operator<` to use references instead of pointers, aligning with standard C++ practices and enhancing safety. This change supports accurate timestamp-based sorting in simulations and reconstructions.

Let me know if you need any further modifications or additional information!