Context.tmethod lookup : var -> Bil.result optionself#lookup var evaluate variable var to a value that was previously bound to it. Returns None if it is unbound.
method update : var -> Bil.result -> 'sself#update var x bind variable var to value x. Returns a a context updated with the new binding.
method bindings : (var * Bil.result) seqself#bindings returns a current list of bindings. Useful, for debugging and introspection.