%================== 1 var =====================

% while (x > 0) x = -2x + 10
entry1_1(X) :- 
    {X>=1, X1= -2*X+10}, entry1_1(X1).

% while (x > 1)  -2x = x
entry1_3(X) :- 
    {X >= 2, -2*X1=X}, entry1_3(X1).

% while (x > 1) 2x =< x
entry1_4(X) :- 
    {X>=2, 2*X1=<X}, entry1_4(X1).

%================== 2 var =====================

% while (x > 0 and x < y)    x = 2x    y++
entry2_7(X,Y) :- 
    {X>=1, X+1=<Y, X1=2*X, Y1=Y+1}, 
    entry2_7(X1,Y1).

% while (x > 0)    x = x - 2y    y++
entry2_8(X,Y) :- 
    {X>=1, X1=X-2*Y, Y1=Y+1},entry2_8(X1,Y1).

% while (x > 0 and x < n)  x = -x + y - 5  y = 2y
entry2_9(X,Y,N) :- 
    {X>=1, X+1=<N, X1= -X+Y-5, Y1=2*Y, N1=N},
    entry2_9(X1,Y1,N1).

% while (x > 0 and y < 0)    x = x + y    y--
entry2_10(X,Y) :- 
    {X>=1, Y+1=<0, X1=X+Y, Y1=Y-1}, 
    entry2_10(X1,Y1).

% while (x > y)  x = x - y   y =< 2  y >= 1
entry2_20(X,Y) :- 
   {X>=Y+1, X1=X-Y, Y=< 2, Y>=1, Y1=Y},
   entry2_20(X1,Y1).