Recursive Descent Parser

A recursive descent parser that produces a parse tree. This project is used only as a way to understand and learn about some of the components that make up a compiler. This is not designed to be a functional language.

Program.txt is a simulated language that the parser will analyze and produce errors as necessary. Upon encoutering an error, the line number of the program with the error will be produced along with some description of the error. If the program grammer and syntax are correct, there should be no output.

Language Grammer

• Rule 01: PROGRAM -> program { DECL_SEC STMT_SEC }
• Rule 02: DECL_SEC -> DECL | DECL DECL_SEC
• Rule 03: DECL -> ID_LIST : Float;
• Rule 04: ID_LIST -> ID | ID , ID_LIST
• Rule 05: ID -> (a|b|c|...| z | A | ... | Z)+
• Rule 06: STMT_SEC -> STMT | STMT STMT_SEC
• Rule 07: STMT -> ASSIGN | IFSTMT | WHILESTMT | REPEAT | INPUT | OUTPUT
• Rule 08: ASSIGN -> ID := EXPR ;
• Rule 09: IFSTMT -> if COMP { STMT_SEC } | if COMP { STMT_SEC } else { STMT_SEC }
• Rule 10: WHILESTMT -> while COMP { STMT_SEC }
• Rule 11: REPEAT -> repeat { STMT_SEC } until COMP ;
• Rule 12: INPUT -> cin << ID_LIST ;
• Rule 13: OUTPUT -> cout >> ID_LIST ;
• Rule 14: EXPR -> FACTOR | FACTOR + EXPR | FACTOR - EXPR
• Rule 15: FACTOR -> OPERAND | OPERAND * FACTOR | OPERAND / FACTOR | OPERAND % FACTOR
• Rule 16: OPERAND -> FLOAT | ID | ( EXPR )
• Rule 17: FLOAT -> (0 | 1 | ... | 9)+ . (0 | 1| … | 9)+
• Rule 18: COMP -> ( OPERAND = OPERAND ) | ( OPERAND <> OPERAND ) | ( OPERAND > OPERAND ) | ( OPERAND < OPERAND )

Lexemes

• Reserved words: program, begin, end, if, then, else, input, output, Float, while, loop.
• Operators: := (assignment), < (less than), > (greater than), = (equals), <> (not equals), + (add), - (subtract), * (multiply).
• Other: ; (end statment).