This paper describes an integrated system for developing regular array designs based on the block description language Ruby. Ruby supports concise design description and formal veri®cation. A parametrised Ruby description can be used in simulating, re®ning and visualising designs, and in compiling hardware implementations such as ®eld programmable gate arrays. Our system enables rapid design production, while good design quality is achieved by (a) the ecient instantiation of device-speci®c libraries, (b) the size optimisation of bit-level components using the design re®ner, and (c) the exploitation of regularity information at source level in the library composition process. The development and implementation of several median ®lters are used to illustrate the system. Ó