The K programming language (as implemented in kparc, kdb+, kona and oK), an cousin of APL, does away with explicit matrices, and has 3 basic types: atom=scalar,

The K programming language (as implemented in kparc, kdb+, kona and oK), an cousin of APL, does away with explicit matrices, and has 3 basic types: atom=scalar, list=vector and dict=mapping. A 2d matrix is implemented as a vector of (vectors of all the same dimensions); a 3d matrix is implemented as a vector of (matrices all of the same dimensions). This greatly simplified the entire language - both semantics and implementation.