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EBNF NotationSpec.EBNFNotation HistoryHide minor edits - Show changes to output 2015-09-21 17:43
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The syntax of PIM Modula-2 was formally defined in an extended version of Backus-Naur Formalism, known as Wirth EBNF, in which brackets and braces are used to denote optional and repeating syntactic entities. For the formal definition of the revised Modula-2 language we use a slightly different version of EBNF which employs parentheses and modifier suffixes instead. to:
The syntax of PIM Modula-2 was formally defined in an extended version of Backus-Naur Formalism, known as Wirth EBNF, in which brackets and braces are used to denote optional and repeating syntactic entities. For the formal definition of the revised Modula-2 language we use a '''slightly different version of EBNF''' which employs parentheses and modifier suffixes instead. 2015-09-19 16:03
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Reserved-Word := Uppercase-Letter* ; Deleted lines 109-117:
non-Terminal := lowercase-Letter Letter* ; Terminal := Uppercase-Letter Letter* ; Reserved-Word := Uppercase-Letter* ; 2015-09-19 16:01
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non-Terminal := lowercase-Letter Letter* ; Terminal := Uppercase-Letter Letter* ; 2015-09-18 10:58
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!!!A Notation to Describe the Syntax of Modula-2 The syntax of PIM Modula-2 was formally defined in an extended version of Backus-Naur Formalism, known as Wirth EBNF, in which brackets and braces are used to denote optional and repeating syntactic entities. For the formal definition of the revised Modula-2 language we use a slightly different version of EBNF which employs parentheses and modifier suffixes instead. Each EBNF rule defines exactly one symbol and is terminated by a semicolon. Names of symbols start with a letter which may be followed by letters, digits, hyphens and low lines. Names may not contain whitespace. Terminal symbols are denoted by names which start with an uppercase letter. Non-terminal symbols are denoted by names which start with a lowercase letter. Literals are enclosed in double or single quotes. By convention, reserved words of the target language are denoted in all-uppercase letters. EBNF production rules take the following general forms: !!!!Synonym [@ foo := bar ; @] [-Symbol @@foo@@ is defined as a synonym for symbol @@bar@@.-] !!!!Sequence [@ foo := bar baz ; @] [-Symbol @@foo@@ is defined as a sequence of symbol @@bar@@ followed by symbol @@baz@@.-] !!!!Alternative [@ foo := bar | baz ; @] [-Symbol @@foo@@ is defined as an alternative, either symbol @@bar@@ or symbol @@baz@@, but not both.-] !!!!Option [@ foo := bar? ; @] [-Symbol @@foo@@ is defined by zero or one occurrence of symbol @@bar@@.-] !!!!Repetition [@ foo := bar+ ; @] [-Symbol @@foo@@ is defined by one or more occurrences of symbol @@bar@@.-] !!!!Optional Repetition [@ foo := bar* ; @] [-Symbol @@foo@@ is defined by zero or more occurrences of symbol @@bar@@.-] !!!!Grouping Parentheses may be used to group syntactic entities on the right hand side of an EBNF rule. A group may be followed by a @@?@@, @@+@@ or @@*@@ modifier which then applies to the group as a whole. [@ foo := bar ( baz | bam ) ( “,” boo )* ; @] [-Symbol @@foo@@ is defined by an occurrence of symbol @@bar@@ followed by an alternative of symbol @@baz@@, or symbol @@bam@@ followed by zero or more occurrences of literal @@“,”@@ and symbol @@boo@@.-] !!!EBNF defined in EBNF [@ syntax := statement* ; statement := symbol-id “:=” expression “;” ; expression := term ( “|” term )* ; term := factor+ ; factor := ( symbol-id | literal | literal-range | group ) ( “?” | “+” | “*” )* ; group : = “(“ expression “)” ; symbol-id := terminal-id | non-terminal-id ; terminal-id := Uppercase-Letter ( Uppercase-Letter | Digit | “-” | “_” )* ; non-terminal-id := Lowercase-Letter ( Letter | Digit | “-” | “_” )* ; literal := ( ‘“‘ ( Character | “‘” )+ ‘“‘ ) | ( “‘“ ( Character | ‘“’ )+ “‘“ ) ; literal-range := literal “..” literal ; Letter := Uppercase-Letter | Lowercase-Letter ; Uppercase-Letter := “A” .. “Z” ; Lowercase-Letter := “a” .. “z” ; Digit := “0” .. “9” ; Character := Letter | Digit | “ “ | “!” | “#” | “$” | “%” | “&” | “(“ | “)” | “*” | “+” | “,” | “-” | “.” | “/” | “:” | “;” | “<“ | “=” | “>” | “?” | “@” | “[“ | “]” | “^” | “_” | “`” | “{“ | “|” | “}” | “~” ; Reserved-Word := Uppercase-Letter* ; @] |