?- start.
		input a= 3.
		input b= 4.
		input c= 5.
		These numbers are the edges of a triangle.
		true.

                start:- write('input a= '),read(A),
                        write('input b= '),read(B),
                        write('input c= '),read(C),
                        A >= 0,B >= 0,C >= 0,   /* must be positive */
                        A < B + C,B < C + A,C < A + B, 
                        write('These numbers are the edges of a triangle.').