On detecting total and partial symmetry of switching functions

A method is presented for identifying total or partial symmetry of switching functions based on the application of the principle of residue test. The invariance of a switching function under a single interchange of two variables can be readily detected from the equality of some of the residues of expansions about these two variables. This procedure of detecting invariance is directly applied for the identification of total or partial symmetry of a switching function whose variables of symmetry are either all unprimed, all primed, or of mixed nature.