Hi, I have written an interpreter that operates on the lambda calculus augmented with letrec, constructors, case, primitive objects, and builtin operations. I'd like to display the internal state of the intepreter at various points so that I can, um, debug the "programs" that I've written. Currently I've got about 3500 nodes, and I'm dumping a graph that I format using the 'dot' program in graphviz. I might have "let x = 1+2 in x*x" represented as. x/1: <2>+<3> 2: 1.0 3: 2.0 4: <1>*<1> where <1>, <2>, <3>, represent various memory locations. I can display this in graphviz, where each node is a rectangle containing text like "<1>*<1>" and there are arrows from the rectangle to <1>. This works as long as the number of nodes isn't very large. However, it would be nice to know of any programs that are better suited for this. For example, if I could write <>*<> and draw arrows from the placeholders "<>" to the memory location being referenced, that would be easier to read. This is done here http://en.wikibooks.org/wiki/Haskell/Graph_reduction to illustrate that 'square (1+2)' doesn't evaluate 1+2 twice. Any ideas? thanks, -BenRI P.S. If this is too off-topic, please let me know.