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# PeOP

indicates an argument to a PETSc function is optional and one can pass `NULL` instead. This is used by the Fortran API generator

## Example

       PetscErrorCode XXXX(Vec v, PeOp PetscObject obj, PeOp PetscInt *idx, PeOp PetscInt *array[])

## Notes

This is not part of the PETSc public API and should only be used in PETSc source code.

Put this in the function declaration in front of each variable that is optional

## Developer Note

Shortened form of PETSc optional

## See Also

`PeNS`, `PeNSS`, `PeCtx`, `PetscInitialize()`

## Level

developer

## Location

include/petscsys.h

Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages