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COMPILER Oberon
(* A grammar for Oberon *)
CHARACTERS
eol = CHR(13) .
letter = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
digit = "0123456789" .
hexDigit = digit + "ABCDEF" .
noQuote = ANY - '"' - eol .
IGNORE CHR(9) .. CHR(13)
COMMENTS
FROM "(*" TO "*)" NESTED
TOKENS
ident = letter { letter | digit } .
integer = digit { digit } | digit { hexDigit } "H" .
real = digit { digit } "." { digit }
[ ("E" | "D") [ "+" | "-" ] digit { digit } ] .
CharConstant = digit { hexDigit } "X" .
string = '"' { noQuote } '"' .
PRODUCTIONS
Oberon = module .
number = integer | real .
identdef = ident [ "*" ] .
qualident = [ ident "." ] ident .
ConstantDeclaration = identdef "=" ConstExpression .
ConstExpression = expression .
TypeDeclaration = identdef "=" type .
type = qualident | ArrayType | RecordType | PointerType | ProcedureType .
ArrayType = "ARRAY" length { "," length } "OF" type .
length = ConstExpression .
RecordType = "RECORD" [ "(" BaseType ")" ] FieldListSequence "END" .
BaseType = qualident .
FieldListSequence = FieldList { ";" FieldList } .
FieldList = [ IdentList ":" type ] .
IdentList = identdef { "," identdef } .
PointerType = "POINTER" "TO" type .
ProcedureType = "PROCEDURE" [ FormalParameters ] .
VariableDeclaration = IdentList ":" type .
designator = qualident { "." ident | "[" ExpList "]" | "(" qualident ")" | "^" } .
ExpList = expression { "," expression } .
expression = SimpleExpression [ relation SimpleExpression ] .
relation = "=" | "#" | "<" | "<=" | ">" | ">=" | "IN" | "IS" .
SimpleExpression = [ "+" | "-" ] term { AddOperator term } .
AddOperator = "+" | "-" | "OR" .
term = factor { MulOperator factor } .
MulOperator = "*" | "/" | "DIV" | "MOD" | "&" .
factor = number | CharConstant | string | "NIL" | set
| designator [ ActualParameters ]
| "(" expression ")" | "~" factor .
set = "{" [ element { "," element } ] "}" .
element = expression [ ".." expression ] .
ActualParameters = "(" [ ExpList ] ")" .
statement = [ assignment | ProcedureCall | IfStatement |
CaseStatement | WhileStatement | RepeatStatement |
LoopStatement | WithStatement | "EXIT" |
"RETURN" [ expression ] ] .
assignment = designator ":=" expression .
ProcedureCall = designator [ ActualParameters ] .
StatementSequence = statement { ";" statement } .
IfStatement = "IF" expression "THEN" StatementSequence
{ "ELSIF" expression "THEN" StatementSequence }
[ "ELSE" StatementSequence ] "END" .
CaseStatement = "CASE" expression "OF" case { "|" case }
[ "ELSE" StatementSequence ] "END" .
case = [ CaseLabelList ":" StatementSequence ] .
CaseLabelList = CaseLabels { "," CaseLabels } .
CaseLabels = ConstExpression [ ".." ConstExpression ] .
WhileStatement = "WHILE" expression "DO" StatementSequence "END" .
RepeatStatement = "REPEAT" StatementSequence "UNTIL" expression .
LoopStatement = "LOOP" StatementSequence "END" .
WithStatement = "WITH" qualident ":" qualident "DO" StatementSequence "END" .
ProcedureDeclaration = ProcedureHeading ";" ProcedureBody ident .
ProcedureHeading = "PROCEDURE" [ "*" ] identdef [ FormalParameters ] .
ProcedureBody = DeclarationSequence [ "BEGIN" StatementSequence ] "END" .
ForwardDeclaration = "PROCEDURE" "^" ident [ "*" ] [ FormalParameters ] .
DeclarationSequence = { "CONST" { ConstantDeclaration ";" }
| "TYPE" { TypeDeclaration ";" }
| "VAR" { VariableDeclaration ";" } }
{ ProcedureDeclaration ";"
| ForwardDeclaration ";" } .
FormalParameters = "(" [ FPSection { ";" FPSection } ] ")" [ ":" qualident ] .
FPSection = [ "VAR" ] ident { "," ident } ":" FormalType .
FormalType = { "ARRAY" "OF" } (qualident | ProcedureType) .
ImportList = "IMPORT" import { "," import } ";" .
import = ident [ ":=" ident ] .
module = "MODULE" ident ";"
[ ImportList ] DeclarationSequence
[ "BEGIN" StatementSequence ] "END" ident "." .
END Oberon.
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