[petsc-dev] inconsistency for its own sake?

[Barry Smith]

   The thing I don't like about typedef's for function pointers is that they do not display the calling sequencing in the code 

  For example  from

> typedef struct _n_TSDM *TSDM;
> struct _n_TSDM {
>   TSRHSFunction rhsfunction;

  or 

   PetscErrorCode TSSetRHSFunction(TS ts, TSRHSFunction rhsfunction)

  I have no freaking idea what the calling sequence of rhsfunction is. but with 

> typedef struct _n_TSDM *TSDM;
> struct _n_TSDM {
>   PetscErrorCode (*TSRHSFunction)(TS,PetscReal,Vec,Vec,void*);

 or

    PetscErrorCode TSSetRHSFunction(TS ts, PetscErrorCode (*TSRHSFunction)(TS,PetscReal,Vec,Vec,void*);

boom I know exactly the calling sequence.

   Maybe there is some way we can do manual pages for these beasties and consistency of names in different locations so we get the best of both worlds?

   Barry



On Nov 25, 2012, at 3:58 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Sun, Nov 25, 2012 at 4:42 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> typedef struct _n_KSPDM *KSPDM;
> struct _n_KSPDM {
>   PetscErrorCode (*computeoperators)(KSP,Mat,Mat,MatStructure*,void*);
>   PetscErrorCode (*computerhs)(KSP,Vec,void*);
>   PetscErrorCode (*computeinitialguess)(KSP,Vec,void*);
> 
> typedef struct _n_SNESDM *SNESDM;
> struct _n_SNESDM {
>   PetscErrorCode (*computefunction)(SNES,Vec,Vec,void*);
>   PetscErrorCode (*computegs)(SNES,Vec,Vec,void*);
>   PetscErrorCode (*computejacobian)(SNES,Vec,Mat*,Mat*,MatStructure*,void*);
> 
>   /* objective */
>   PetscErrorCode (*computeobjective)(SNES,Vec,PetscReal*,void*);
> 
> 
> typedef struct _n_TSDM *TSDM;
> struct _n_TSDM {
>   TSRHSFunction rhsfunction;
>   TSRHSJacobian rhsjacobian;
> 
>   TSIFunction ifunction;
>   TSIJacobian ijacobian;
> 
> The PETSc style guide says  to avoid typedef of function pointers unless there is a damn good reason to use them (or it should);
> 
> Can we revisit this choice in the interest of writing one man page that documents the assumptions that one can make about a callback routine? I hate duplicating the same information in TS{Set,Get}IFunction() and DMTS{Set,Get}IFunction(). Also, if a typedef is used everywhere, we can more reliably find all places that depend on it. (using grep or M-x gtags-find-symbol).
>  
> but why use them for TS but not for SNES or KSP functions?
> 
> Because they were already defined for use with TSSetIFunction()/TSGetIFunction().