MAKEFILE:
=========

<makefile> ::= '(' + "makefile" + <makerule-clause>* + ')'

<makerule-clause> ::= <rule-clause> 
		      | <md5-clause> 
		      | <always-clause> 
		      | <once-clause>

<rule-clause> ::= '(' + <rule-clause-identifier>
		      + <target-spec> 
	              + <prereq-spec> 
		      + <action-spec> + ')'

<md5-clause> ::= '(' + <md5-clause-identifier>
                     + <target-spec> 
	             + <prereq-spec> 
		     + <action-spec> + ')'

<always-clause> ::= '(' + <always-clause-identifier>
		        + <target-spec> 
	                + <prereq-spec> 
		        + <action-spec> + ')'

<once-clause> ::= '(' + <once-clause-identifier>
		      + <target-spec> 
	              + <prereq-spec> 
		      + <action-spec> + ')'

<rule-clause-identifier> ::= "rule" 
                             | "makefile-rule" 
                             | "is-out-of-date?"

<md5-clause-identifier> ::= "md5" 
                            | "rule-md5" 
                            | "fp-changed?"

<always-clause-identifier> ::= "always" 
                               | "rule-always" 
                               | "phony" 
                               | "is-out-of-date!"

<once-clause-identifier> ::= "once" 
                             | "rule-once"

<target-spec> ::= <target> | <target-list>
<target> ::= <filename>
<target-list> ::= '(' + <filename>+ + ')'

<prereq-spec> ::= <prereq> | <prereq-list>
<prereq> ::= <filename>
<prereq-list> ::= '(' + <filename>* + ')'

<action-spec> ::= <action> | <action-list>
<action> ::= '(' + <thunk>* + ')'
<action-list> ::= '(' + <action>+ + ')'

<filename> ::= '"' + {<dir-separator> + { 'a'-'z''A'-'Z''0'-'9' ... }+ }+ + '"'