1. The RelView system in action (full-size):

The RelView system.

2. Breakpoint reached while executing the following program: 

RecProg(R,v)
	DECL Ret,p
	BEG IF empty(v) THEN Ret = R
	    ELSE
		p = point(v);
	      Ret = R*RecProg(R,v&-p)
	    FI;
	    ASSERT(RecProgBreak,FALSE())
	    RETURN Ret
        END.
(Breakpoint are assertions, which always fail.)

Breakpoint.

3. The debugger window for RecProg (full-size).

The RelView system.