Compiler

lexer

• comments: Comments starts with // characters and ends with the end of line character.
• keywords: The keywords given in the grammar: int real if then else while
• identifiers: An identifier starts with a letter and continues with a letter or digit. A keyword cannot be an identifier, and the maximum length of an identifier is 64 characters.
• operators: The followings are operators: + - / * = == < <= > >= !=
• delimiters: The followings are delimeters: ( ) { } ;
• numbers: The numbers are defined as follows:
• digit <- 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
• intnumber <- digit+ (the maximum integer number is 231)
• exponent <- (E|e) ( + | - | null ) digit+ (the maximum exponent value is 128)
• fraction <- . digit+
• realnumber <- digit+ exponent | digit+ fraction ( exponent | null )

grammar

• program -> decls compoundstmt
• decls -> decl ; decls | null
• decl -> int ID = INTNUM | real ID = REALNUM
• stmt -> ifstmt | assgstmt | compoundstmt
• compoundstmt -> { stmts }
• stmts -> stmt stmts | null
• ifstmt -> if ( boolexpr ) then stmt else stmt
• assgstmt -> ID = arithexpr ;
• boolexp -> arithexpr boolop arithexpr
• boolop -> < | > | <= | >= | ==
• arithexpr -> multexpr arithexprprime
• arithexprprime -> + multexpr arithexprprime | - multexpr arithexprprime | null
• multexpr -> simpleexpr multexprprime
• multexprprime -> * simpleexpr multexprprime | / simpleexpr multexprprime | null
• simpleexpr -> ID | INTUM | REALNUM | ( arithexpr )