This file describes the overall syntax of kmp-scheme.

see ~gjr/work/liar94/text/forms.txt:

;;; -*- Text -*-

;; Output of input stage (except for LETREC).

<expression> = 
  (QUOTE <object>)			; constant object reference
| (LOOKUP <name>)			; variable reference
| (LAMBDA <lambda-list> <expression>)	; procedural abstraction
| (LET (<binding>*) <expression>)	; simple variable binding
| (DECLARE <declaration>*)		; ??
| (CALL <expression> <expression>+)	; procedure application
| (BEGIN <expression>*)	                ; sequential execution
| (IF <expression> <expression> <expression>)
					; conditional execution
;; The following is introduced by "assconv.scm", it need not be handled before
| (LETREC (<binding>*) <expression>)	; mutually recursive bindings:
					; only lambda-expressions allowed.
;; The following need not be handled after "assconv.scm"
| (SET! <name> <expression>)		; variable assignment
;; The following need not be handled after "expand.scm"
| (OR <expression> <expression>		; conditional execution
| (DELAY <expression>)			; promise construction
| (UNASSIGNED? <name>)			; variable initialization test
;; The following need not be handled after "envconv.scm"
| (ACCESS <name> <expression>)		; variable reference in computed env.
| (DEFINE <name> <expression>)		; variable definition
| (THE-ENVIRONMENT)			; environment reification
| (IN-PACKAGE <expression> <expression>)
					; evaluation in computed environments

<binding> = (<name> <expression>)
					; LET allows only simple expressions
					; LETREC allows only LAMBDA expressions

<lambda-list> = (<name>* <optionals> <rest> <aux>)

<optionals>   = <empty>
		| #!optional <name>+

<rest>        = <empty>
		| #!rest <name>

<aux>         = <empty>
		| #!aux <name>+

<aux> is eliminated in expand.scm.  It is not handled afterwards.

CALL expressions have at least two subexpressions:
- operator
- continuation ('#f until cps)

<thing>* means 0 or more <thing>
<thing>+ means 1 or more <thing>