<Emphasis Type="Italic">G</Emphasis>-projectable and Λ-projectable binary linear block codes

The binary 24,12,8] Golay code has projection O onto the quaternary 6,3,4] hexacode 9] and the 32,16,8] Reed-Muller code has projection E onto the quaternary self-dual 8,4,4] code 6]. Projection E was extended to projection G in 8]. In this paper we introduce a projection, to be called projection Λ, that covers projections O, E and G. We characterise G-projectable self-dual codes and Λ-projectable codes. Explicit methods for constructing codes having G and Λ projections are given and several so constructed codes that have best known optimal parameters are introduced.