T =: {{ 0.5*y*y+1 }} P =: {{ 0.5*y*_1+3*y }} H =: {{ y*_1+2*y }} limit =: 1e5 NB. A guess that works 'Ts Ps Hs' =: (T;P;H)i.limit isP =: e.&Ps isH =: e.&Hs isPH =: isP*.isH problem45 =: Ts{~3}.I.isPH Ts