mekso binary operator: generate span; outputs span(X_{1, X}= span_{X}; set of all (finite) sums of terms of form c v, where v is an element of algebraic structure X_{1} (wherein scalar multiplication and summation is defined), and c is a scalar belonging to ring X_{2}.

For example, the span of vectors v_{1} and v_{2} in vector space V over the field of exactly all real numbers R has X_{1 }= Intersect(V, Set(v_{1, v} and X_{2 }= R and yields output Set(c_{1 v} in R for alli), where scalar multiplication and vector addition are as defined in V.