Acyclic Convolution in Matlab or Octave

In Matlab or Octave, the conv function implements acyclic convolution:

octave:1> conv([1 2],[3 4])
ans =
   3  10   8

Note that it returns an output vector which is long enough to accommodate the entire result of the convolution, unlike the filter primitive, which always returns an output signal equal in length to the input signal:

octave:2> filter([1 2],1,[3 4])
ans =
   3  10
octave:3> filter([1 2],1,[3 4 0])
ans =
   3  10   8