It would be nice to make this work:

    Macaulay2, version 1.3.1.1
    with packages: ConwayPolynomials, Elimination, IntegralClosure, LLLBases, PrimaryDecomposition, ReesAlgebra, SchurRings, TangentCone

    i1 : R = QQ[a]

    o1 = R

    o1 : PolynomialRing

    i2 : S = R[b]

    o2 = S

    o2 : PolynomialRing

    i3 : map(R,S,{b=>a})
    stdio:3:1:(3):[0]: error: destinations not specified for every generator
