networks,table->function: Store the function in a local binding.

This avoids reconstructing the function from the table every time the
lambda is called.

networks.rkt

@@ -425,7 +425,8 @@
 ;;; meaning that it may be sometimes more expensive to compute than by
 ;;; using an direct symbolic implementation.
 (define (table->function table)
-  (λ args ((table->function/list table) args)))
+  (let ([func (table->function/list table)])
+    (λ args (func args))))
 
 ;;; Like table->function, but the produced function accepts a single
 ;;; list of arguments instead of individual arguments.