The dispersion properties of edge modes supported by linear discontinuities of surface impedance planes, i.e., the so-called line waves, are studied here by means of a full-wave numerical approach based on the method of moments in the spectral domain. The proposed formulation, based on entire-domain basis functions defined on a half line, is both versatile and computationally efficient; its accuracy is validated through a comparison against analytical results obtained with the Sommerfeld-Maliuzhinets method.