The routine returns true if the point f or the list/set of points f is on line l; false if it is not; and FAIL if it is unable to reach a conclusion.

In case of FAIL, if the third optional argument is given, the condition that makes f on line l is assigned to this argument. It will be either of the form  or of the form  where expr, expr_i are Maple expressions.

The command with(geometry,IsOnLine) allows the use of the abbreviated form of this command.

IsOnLine:   "hint: the following conditions must be satisfied: {-2/5+b = 0, -1/2+a = 0}"