The rules are not made explicit for what happens when a verb fails when applied to a fill cell, but I have deduced by experiment that the interpreter behaves as if the failing result were a scalar numeric. Thus:
plus =: 4 : 'x + y'"0 $ 5 plus"1 (0 1 $' ') 0 Correct: 5 +"1 (1 $ ' ') failed, so ($0) was used as the result shape from the fill-cell, and that was extended with the frame (,0) to give a final result shape of ,0 . $ 5 +"1 (0 1 $' ') 0 1 Incorrect: should be the same result as above, but apparently special code for the + verb did not take into account the subtleties of fill-cell processing and assigned the result to have the same shape as the array operand. Henry Rich ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
