# sc_SpatialMOPairIter_eq man page

sc::SpatialMOPairIter_eq — **SpatialMOPairIter_eq** gives the ordering of same-spin and different-spin orbital pairs if both orbitals of the pairs are from the same space.

## Synopsis

`#include <pairiter.h>`

Inherits **sc::SpatialMOPairIter**.

### Public Member Functions

SpatialMOPairIter_eq(constRef<MOIndexSpace> &space1)Initialize an iterator for the given MO spaces.

voidstart(const int ij_offset=0)Initialize the iterator assuming that iteration will start with pair ij_offset.

voidnext()Move to the next pair.operator int() constReturns nonzero if the iterator currently hold valid data.

intnij_aa() constReturns the number of functions in alpha-alpha space.

intnij_ab() constReturns the number of functions in alpha-beta space.

intij_aa() constReturns compound index ij for alpha-alpha case.

intij_ab() constReturns compound index ij for alpha-beta case.

intij_ba() constReturns compound index ij for beta-alpha case.

### Additional Inherited Members

## Detailed Description

**SpatialMOPairIter_eq** gives the ordering of same-spin and different-spin orbital pairs if both orbitals of the pairs are from the same space.

It iterates over all i >= j combinations (total of (ni_+1)*(ni_+2)/2 pairs).

## Member Function Documentation

### int sc::SpatialMOPairIter_eq::ij_aa () const [inline], [virtual]

Returns compound index ij for alpha-alpha case. The i == j combination doesn't make sense, so **ij_aa()** will return -1 for such pairs.

Implements **sc::SpatialMOPairIter**.

## Author

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