⌹ — Matrix inverse / Matrix divide⌹Y gives an inverse, or a full-column-rank least-squares pseudoinverse. Scalars reciprocate.
⌹2x ⍝ 1r2
⌹2 2⍴1x 0x 0x 2x ⍝ 2 2⍴1x 0x 0x 1r2
X⌹Y solves Y+.×Z = X, using least squares when overdetermined.
3x 5x 7x⌹3 2⍴1x 1x 1x 2x 1x 3x ⍝ 1x 2x
All-exact inputs use rational elimination; approximate real/complex inputs use SVD.
DOMAIN: singular or underdetermined system, non-finite input.