Naming of Variables

All non-trivial data must be given descriptive names, although extremely long names are discouraged. For example, compound variable names like num_atoms or atom_orbit_degen should be preferred to nat or atord, so that non-specialists could understand the code. It is also a good idea to put a descriptive comment where a non-trivial variable is declared. However, simple loop indices should generally be named i,j,k or p,q,r.

PSI3 programs have certain conventions in place for names of most common variables, as shown in the Table 1.

Table 1: Some Variable Naming Conventions in PSI3

Quantity	Variable(s)
Number of atoms	na, natom, num_atoms
Number of atoms * 3	natom3, num_atoms3
Nuclear repulsion energy	enuc, repnuc
SCF energy	escf
Number of atomic orbitals	nbfao, num_ao
Number of symmetry orbitals	nbfso, num_so
Size of lower triangle
of AO's, SO's	nbatri, nbstri; ntri
Input file pointer	infile
Output file pointer	outfile
Offset array	ioff
Number of irreps	num_ir, nirreps
Open-shell flag	iopen
Number of orbitals per irrep	orbs_per_irrep, orbspi, mopi
Number of closed-shells
per irrep	docc, clsd_per_irrep, clsdpi
Number of open-shells
per irrep	socc, open_per_irrep, openpi
Orbital symmetry array	orbsym