Semantic Model (part 4)

For the dependency/action tree, we will define 
an auxiliary Ocaml recursive datatype:

type file = string
type actions = string list
type rule = Rule of (file * rule list * actions)

Example Makefile Fragment:

lisp.o: lisp.c
       gcc -c $<
emacs: emacs.c lisp.o buffer.h
       gcc -o $@ emacs.c lisp.o

Becomes Ocaml Value:

Rule ("emacs", 
  [ Rule ("emacs.c", [], []);
    Rule ("lisp.o", 
      [ Rule ("lisp.c", [], []) ],
      [ "gcc -c lisp.c" ] );
    Rule ("buffer.h", [] []); ],
  [ "gcc -o emacs emacs.c lisp.o" ] )