MODULA-2 Subset Grammar Rules

This project implements a recursive descent parser for a subset of the MODULA-2 programming language. -The grammar rules define the structure of MODULA-2 programs using production rules. The parser is designed to recognize and parse valid MODULA-2 code based on the specified grammar.

Production rules:

The parser adheres to the following grammar rules:

Module Declaration

• module-decl → module-heading declarations procedure-decl block name .
• module-heading → module name ;
• block → begin stmt-list end
• declarations → const-decl var-decl
• const-decl → const const-list | ε
• const-list → ( name = value ; )*
• var-decl → var var-list | ε
• var-list → ( var-item ; )*
• var-item → name-list : data-type
• name-list → name ( , name )*
• data-type → integer | real | char

Procedure Declaration

• procedure-decl → procedure-heading declarations block name ;
• procedure-heading → procedure name ;
• stmt-list → statement ( ; statement )*
• statement → ass-stmt|read-stmt | write-stmt | if-stmt | while-stmt | repeat-stmt | exit-stmt | call-stmt | ε

Assignment Statement

• ass-stmt → name := exp

Expression

• exp → term ( add-oper term )*
• term → factor ( mul-oper factor )*
• factor → ( exp ) | name | value
• add-oper → + | -
• mul-oper → * | / | mod | div

Read Statement

• read-stmt → readint ( name-list ) | readreal ( name-list ) | readchar ( name-list ) | readln

Write Statement

• write-stmt → writeint ( write-list ) | writereal ( write-list ) | writechar ( write-list ) | writeln
• write-list → write-item ( , write-item )*
• write-item → name | value

If Statement

• if-stmt → if condition then stmt-list elseif-part else-part end
• elseif-part → ( elseif condition then stmt-list )*
• else-part → else stmt-list | ε

While Statement

• while-stmt → while condition do stmt-list end

Repeat Statement

• repeat-stmt → loop stmt-list until condition

Exit Statement

• exit-stmt → exit

Call Statement

• call-stmt → call name (* This is a procedure name *)

Condition

• condition → name-value relational-oper name-value
• name-value → name | value
• relational-oper → = | |= | < | <= | > | >=

Identifier

• name → letter ( letter | digit )*

Values

• value → integer-value | real-value
• integer-value → digit ( digit )*
• real-value → digit ( digit )* . digit ( digit )*

Note

The tokens in bold are reserved words or standard identifiers (library functions or procedures).