EBNF - Syntax of SIMULA 67


  1	<program> :: {<block prefix>}<block> | {<block prefix>}<compound statement>
  2		<block prefix> ::= <class identifier>{(<actual paremeter list>)}
  3			<block> ::= <block head>;<compound tail>
  4				<block head> ::= <block head>;<declaration> | BEGIN <declaration>

  5	<declaration> ::= <type declaration> | <array declaration> | <switch declaration> | <procedure declaration> | <class declaration> | <external declaration>
  6		<type declaration> ::= <type><identifier list>
  7			<type> ::= BOOLEAN | CHARACTER | INTEGER | REAL | REF(<class declaration>) | TEXT
  8			<identifier list> ::= {<identifier list>,}<identifier>
  9		<array declaration> ::= {<type>} ARRAY <array list>
 10			<array list> ::={<array list>,} <array segment>
 11				<array segment> ::= <identifier list>[<bound pair list>]
 12					<bound pair list> ::= {<bound pair list>,}<arithmetic expression>:<arithmetic expression>
 13		<switch declaration> ::= SWITCH <switch identifier> := <switch list>
 14			<switch identifier> ::= <identifier>
 15			<switch list> ::= {<switch list>,}<designational expression>
 16		<procedure declaration> ::= {<type>} PROCEDURE <procedure heading>;<proceduere body>
 17			<procedure heading> ::= <procedure identifier>{<formal parameter part>;{<mode part>;}<specification part>}
 18				<formal parameter part> ::= (<identifier list>)
 19				<mode part> ::= {<value part>;}<name part> | {<name part>;}<value part>
 20					<value part> ::= VALUE <identifier list>
 21					<name part> ::= NAME <identifier list>
 22				<specification part> ::= {<specification part>;}<specifier><identifier list>
 23					<specifier> ::= {<type>} ARRAY | LABEL | {<virtual part>;}<identifier list>
 24			<procedure body> ::= <statement>
 25		<class declaration> :: {<prefix>} CLASS <class heding>;{<virtual part>;}<class body>
 26			<prefix> ::= <class identifier>
 27			<class heading> ::= <class identifier>{<formal paremeter part>;{<value part>;}<specification part>}
 28				<class identifier> ::= <identifier>
 29			<virtual part> ::= VIRTUAL: <virtual specification part>
 30				<virtual specification part> ::= {<virtual specification part>;}<virtual specifier><identifier list>
 31					<virtual specifier> ::= LABEL | {<type>} PROCEDURE | SWITCH
 32			<class body> ::= <split body> | <statement>
 33				<split body> :: <initial part> INNER; <compound tail>
 34					<initial part> ::= BEGIN | <block head>; | <initial part><statement>
 35		<external declaration> ::= EXTERNAL {<type>} PROCEDURE <external list> | EXTERNAL CLASS <external list>
 36			<external list> ::= {<external list>,}<external item>
 37				<external item> ::= <external identifier> | <identifier> = <external identifier>

 38	<compound statement> ::= BEGIN <compound tail>
 39		<compound tail> ::= END | <statement>;<compound tail>
 40			<statement> ::= <label list><statement> | <conditional statement> | <connection statement> | <repetition statement> | <unconditional statement>
 41				<label list> ::= {<label list>}<label>:
 42					<label> ::= <identifier>
 43				<conditional statement> ::= <if clause><connection statement> | <if clause><repetition statement> | <if clause><unconditional statement>{ELSE <statement>}
 44					<if clause> ::= IF <Boolean expression> THEN
 45				<connection statement> ::= INSPECT <object expression><connection part>{OTHERWISE <statement>}
 46					<connection part> ::= DO <statement> | <selective part>
 47						<selective part> ::= {<selective part>} WHEN <class identifier> DO <statement>
 48				<repetition statement> ::=<for statement> | <while statement>
 49					<for statement> ::= FOR <variable> :- <reference list> DO <statement> | FOR <variable> := <value list> DO <statement>
 50						<reference list> ::= {<reference list>,}<reference expression> {WHILE <Boolean expression>}
 51						<value list> ::= {<value list>,}<value list element>
 52							<value list element> ::= <value expression>{WHILE <Boolean expression>} | <arithmetic expression> STEP <arithmetic expression> UNTIL <arithmetic expression>
 53					<while statement> ::= WHILE <Boolean expression> DO <statement>
 54				<unconditional statement> ::= <basic statement> | {<block prefix>}<block> | {<block prefix>}<compound statement>
 55					<basic statement> ::= <activation statement> | <assignment statement> | <dummy statement> | <goto statement> | <object generator> | <procedure satement>
 56						<activation statement> ::=<activator><object expression>{<scheduling part>}
 57							<activator> ::= ACTIVATE | REACTIVATE
 58							<scheduling part> ::= AT <arithmetic expression>{PRIOR} | DELAY <arithmetic expression> {PRIOR} | BEFORE <object expression> | AFTER <object expression>
 59						<assignment statement> ::= <reference assignment> | <value assignment>
 60							<reference assignment> ::= <reference left part> :- <reference right part>
 61								<reference left part> ::= <variable> | <procedure identifiere>
 62								<reference right part> ::= <reference expression> | <reference assignment>
 63							<value assignment> ::= <value left part> := <value right part>
 64								<value left part> ::= <variable> | <procedure identifier> | <simple text expression>
 65								<value right part> ::= <value expression> | <value assignment>
 66						<dummy statement> ::= <empty>
 67						<goto statement> ::= GOTO <designational expression>
 68						<object generator> ::= NEW <class identifier> {(<actual parameter list>)}
 69						<procedure statement> ::= {<simple reference expression>,}<procedure identifier>{(<actual parameter list>)}
 70							<simple reference expression> ::= <simple object expression> | <simple text expression>
 71							<actual parameter list> ::= {<actual parameter list>,}<actual parameter>
 72								<actual parameter> ::= <expression> | <array identifier> | <procedure identifier> | <switch identifier>
 73									<array identifier> ::= {<simple object expression>.}<identifier>
 74									<procedure identifier> ::= {<simple reference expression>.}<identifier>

 75	<expression> ::= <designational expression> | <reference expression> | <value expression>
 76		<designational expression> ::= <simple designational expression> | <if clause> <simple designational expression> ELSE <designational expression>
 77			<simple designational expression> ::= (<designational expression>) | <labal> | <switch designator>
 78				<switch designator> ::= <switch identifier>[<arithmetic expression>]
 79		<reference expression> ::= <object expression> | <text expression>
 80			<object expression> ::= <simple object expression> | <if clause><simple object expression> ELSE <object expression>
 81				<simple object expression> ::= (<object expression>) | NONE | <function designator> | <local object> | <object generator> | <qualified object> | <variable>
 82					<fuction designator> ::= <procedure identifier> {(<actual parameter list>)}
 83					<local object> ::= THIS <class identifier>
 84					<qualified object> ::= <simple object expression> QUA <class identifier>
 85			<text expression> ::= <simple text expression> | <if clause><simple text expression> ELSE <text expression>
 86				<simple text expression> ::= (<text expression>) | NOTEXT | <function designator> | <variable>
 87			<value expression> ::= <arithmetic expression> | <Boolean expression> | <character expression> | <text value expression>
 88				<simple arithmetic expression> ::= <simple arithmetic expression> | <if clause><simple arithmetic expression> ELSE <arithmetic expression>
 89					<simple arithmetic expression> ::= {{<simple arithmetic expression>}<adding operator>}<arithmetic term>
 90						<adding operator> ::= + | -
 91						<arithmetic term> ::= {<arithmetic term><multiplying operator>}<arithmetic factor>
 92							<multiplying operator> ::= x | / | ÷
 93							<arithmetic factor> ::= {<arithmetic factor>^}<arithmetic primary>
 94								<arithmetic primary> ::= (<arithmetic expression>) | <function designator> | <unsigned number> | <variable>
 95									<unsigned number> ::= <decimal number> {<exponent part>} | <exponent part>
 96										<decimal number> ::= <unsigned integer>{<decimal fraction>} | <decimal fraction>
 97											<unsigned integer> ::= {<unsigned integer>}<digit>
 98											<decimal fraction> ::= .<unsigned integer>
 99										<exponent part> ::= \10{<adding operator>}<unsigned integer>
100				<Boolean expression> ::= <simple Boolean> | <if clause><simple Boolean> ELSE <Boolean expression>
101					<simple Boolean> ::= {<simple Boolean> \equ} <implication>
102						<implication> ::= {<implication> \imp}<Boolean term>
103							<Boolean term> ::= {<Boolean term> \or}<Boolean factor>
104								<Boolean factor> ::= {<Boolean factor> \and}{\not}<Boolean primary>
105									<Boolean primary> ::= (<Boolean expression>} | <logical value> | <function designator> | <relation> | <variable>
106										<logical value> ::= TRUE | FALSE
107										<relation> ::= <qualification relation> | <reference relation> | <value expression>
108											<qualification relation> ::= <simple object expression><qualification tester><class identifier>
109												<qualification tester> ::= IS | IN
110											<reference releation> ::= <object reference relation> | <text reference relation>
111												<object reference relation> ::= <simple object expression> <reference comparator><simple object expression>
112													<reference comparator> ::= == | =/=
113												<text reference relation> ::= <simple text expression><refernce comparator><simple text expression>
114											<value relation> ::= <arithmetic relation> | <character relation> | <text value relation>
115												<arithmetic relation> ::= <simple arithmetic expression><relational operator><simple arithmetic expression>
116													<relational operator> ::= < | ¾ | = | „ | > | ‚
117												<chracter relation> ::= <simple character expression><relational operator><simple character expression>
118												<text value relation> ::= <simple text value><relational operator><simple text value>
119				<character expression> ::= <simple character expression> | <if clause><simple character expression> ELSE <character expression>
120					<simple character expression> ::= (<character expression> | <character constant> | <function designator> | <variable>
121					<character constant> ::= '<any basic symbol>'
122			<text value expression> ::= <simple text value> | <if clause><simple text value> 'ELSE' <text value expression>
123				<simle text value> ::= <simple text expression> | <text constant>
124					<text constant> ::= '<any sequence of basic symbols>'

125	<variable> ::= <simple object expression>.<variable> | <simple variable> | <subscripted variable>
126		<simple variable> ::= <identifier>
127			<identifier ::= {<identifier>}<letter> | <identifier><digit>
128				<letter> ::= A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z
129				<digit> ::= 0|1|2|3|4|5|6|7|8|9|0
130		<subscripted variable> ::= <array identifier>[<subscript list>]
131			<subscript list> ::= {<subscript list>,}<arithmetic expression>




# special signs:

÷    ... division - a line between two dots aligned verticaly  (92)
^    ... power - an up-arrow  (93)
\10  ... power of ten - a lowered "10"  (99)
\equ ... logical equation - three strokes aligned verticaly  (101)
\imp ... logical implication - a "U" turned counter-clockwise  (102)
\or  ... logical or - a sign like a "v"  (103)
\and ... logical and - like a flipped "v"  (104)
\not ... logical not "¬" - like a flipped and conter-clockwise turned "L" (104)