18A. The E grammar
------------------


This is a grammar of E for those who are interested. Don't expect
it to be up to date or otherwise complete/correct though (it should
be quite ok for E upto v2.1b atleast).

lex syntax: regular expressions
parse syntax: own ASF/SDF adaption;

	name	= grammar ident
	"name"	= constant
	()	= grouping
	|	= or
	e*	= 0 or more of e
	e+	= 1 or more of e
	{e s}*	= 0 or more of e separated by s
	{e s}+	= 1 or more of e separated by s
	[e]	= e is optional
	; e	= e is comment :-)



LEX
---



whitespace	= [ \t] 	; also \n if last token is [,+-*/] or similar
		  anything between "/*" and "*/"
		  from "->" to \n
eol		= [;\n]

constant	= [A-Z] ( [A-Z] [A-Za-z0-9_]* )?
builtin		= [A-Z] [a-z] [A-Za-z0-9_]*
ident,objident	= [a-z] [a-zA-Z0-9_]*

num		= [0-9]+	; "-" is separate token
                  $[0-9A-Fa-f]+
		  %[01]+
fnum		= [0-9]*.[0-9]*

stringconst	= anything in ''
charconst	= anything in ""



PARSE
-----


program		= opts globalpart localpart

globalpart	= ( modulestat | defstat | objdecl | constdecl | raisedecl )*
localpart	= ( procdecl | constdecl )+

modulestat	= "MODULE" { conststring "," }+ eol
defstat		= "DEF" vardecllist eol
objdecl		= "OBJECT" ident [ "OF" ident ] eol
                     ( vardecllist eol )+
                  "ENDOBJECT" eol
constdecl	= "CONST" { ( constant "=" constexp ) "," }+ |
		  "ENUM" { ( constant | constant "=" constexp ) "," }+ |
		  "SET" { constant "," }+
procdecl	= [ "EXPORT" ] "PROC" ident "(" argdecllist ")"
                  [ "OF" ident ] [ "HANDLE" ]
                  ( ( "RETURN" | "IS" ) { exp "," }* |
                     eol defstat* stats 
                     [ "EXCEPT" eol stats ]
                     "ENDPROC" { exp "," }* eol )
raisedecl	= "RAISE" { ( constant "IF" builtin "()" compop num ) "," }+
opts		= ( "OPT" { setting "," }+ )*		; machine dependant

vardecllist	= { vardecl "," }+
vardecl		= ident [ "=" num ]
                    [ ":" ( "LONG" | "REAL" | "PTR" "TO" ptrtype ) ] |
                  ident ":" objtype |
                  ident "[" num "]" ":"
                    ( "ARRAY" |
                      "ARRAY" "OF" ptrtype |
                      "STRING" |
                      "LIST" )
argdecllist	= { argdecl "," }+
argdecl		= ident [ "=" defaultarg ]
                    [ ":" ( "LONG" | "REAL" | "PTR" "TO" ptrtype ) ]
ptrtype		= objtype | simpletype
simpletype	= CHAR | INT | LONG
objtype		= ident

stats		= ( ( onelinestat | multlinestat ) eol )*
onelinestat	= exp |
		  lval ":=" exp |
		  { var "," }+ ":=" exp |
		  "IF" exp "THEN" onelinestat "ELSE" onelinestat |
		  "FOR" var ":=" exp "TO" exp [ "STEP" num ]
                     "DO" onelinestat |
		  "WHILE" exp "DO" onelinestat |
		  "RETURN" { exp "," }* |
		  "JUMP" ident |
                  ( "INC" | "DEC" ) var |		; nearly obsolete
		  asm_mnemonic { operand "," }*	|	; machine dependant
		  "INCBIN" stringconst |		; inline asm support
		  simpletype { num "," }+ |
		  "VOID" exp				; obsolete
multlinestat	= "IF" exp eol stats
                     [ ( "ELSEIF" exp eol stats )* ] 
                     [ "ELSE" eol stats ]
                     "ENDIF" |
		  "FOR" var ":=" exp "TO" exp [ "STEP" num ] eol
                     stats "ENDPROC" |
		  "WHILE" exp eol stats "ENDWHILE" |
		  "REPEAT" eol stats "UNTIL" exp |
		  "SELECT" var eol
                     ( "CASE" exp eol stats )+
                     [ "DEFAULT" eol stats ]
                     "ENDSELECT" |
                  "LOOP" eol stats "ENDLOOP"

explist		= { exp "," }+
exp		= [ "-" ] { item binop }+ |
		  exp "BUT" exp
item		= num | fnum | lval | stringconst | charconst |
		  "SIZEOF" objident |
		  "IF" exp "THEN" exp "ELSE" exp |
		  "[" explist "]" [ ":" ptrtype ] |
		  ( builtin | ident ) "(" explist ")" |
		  var ":=" exp |
		  "{" ident "}" |
		  "`" exp |
binop		= mathop | compop | logop
mathop		= "+" | "-" | "*" | "/"
compop		= "=" | "<>" | ">" | "<" | ">=" | "<="
logop		= "AND" | "OR"
constexp	= [ "-" ] { num ( "+" | "-" | "*" | "/" ) }+
lval		= var ( "[" [ exp ] "]" | "." ident )* [ "++" | "--" ] |
		  "^" var [ "++" | "--" ] |
var		= ident
defaultarg	= num