clp with intervals

Dear people,

I have the following CLP program which fails although I do not really
understand why. It fails in SWI-prolog at exactly the same point so I
assume it is me who made a mistake. Maybe somebody can explain, and
possibly suggest a way to solve it.

The problem is that I have a N intervals (in the example below there are
two, A and B) which are contained in an interval C which has the
property that it is a small as possible.  

For completeness I state additional requirements for my application
although they are not all encoded in the sample program:
The C interval is contained in D. Finally at label time I'd like to
specify whether C should be labeled min, max or centered (default:
center)

The last constraint, CX2 #= MinX2 fails. My guess is it has something to
do with the minlist constraint. I am using eclipse 5.7 with the ic
library.

Any help would be greatly appreciated,

	Joost





/*

                 AX1-----AX2  
                                BX1-----BX2
                 CX1--------------------CX2        
        DX1--------------------------------------DX2
        
        
        
*/

run(Out) :-
        CVars = [AX1,AX2,BX1,BX2,CX1,CX2,DX1,DX2],
        Out =
[ax1:AX1,ax2:AX2,bx1:BX1,bx2:BX2,cx1:CX1,cx2:CX2,dx1:DX1,dx2:DX2],

        L = 0, H = 1000,
        AX1 #>= L, AX1 #=< H, AX2 #>= L, AX2 #=< H, AX1 #=< AX2,
        BX1 #>= L, BX1 #=< H, BX2 #>= L, BX2 #=< H, BX1 #=< BX2,
        CX1 #>= L, CX1 #=< H, CX2 #>= L, CX2 #=< H, CX1 #=< CX2,      
        DX1 #>= L, DX1 #=< H, DX2 #>= L, DX2 #=< H, DX1 #=< DX2,
        
        % set size for A , B
        WA = 180,
        WB = 120,
        
        % width A,B
        WA #= AX2 - AX1,        
        WB #= BX2 - BX1,                        
        
        % A before B
        AX2 #=< BX1,

        % C contains A&B
        AX1 #>= CX1, AX2 #=< CX2,
        BX1 #>= CX1, BX2 #=< CX2,
        
        % find minimum  of A & B
        minlist([AX1,BX1],MinX1),
        minlist([AX2,BX2],MinX2),        
        
        % D contains C
        DX1 #=< CX1, DX2 #>= CX2,               
                
        % C fits tightly
        CX1 #= MinX1, 
        CX2 #= MinX2, % This constraint fails!
        
        labeling(CVars),
        true.




-- 
Joost Geurts <Joost.Geurts@cwi.nl>