FACTOR
Accepts an identifier, integer, or parenthesized expression.
Compilers and parsing
A small recursive descent parser written in C
The parser reads a stream of numeric tokens and checks a simplified Pascal style program. Each grammar rule lives in a small C function, so the call structure mirrors the language: factors build terms, terms build expressions, and expressions feed statements.
Parser structure
The functions follow operator precedence
Numeric tokens
Program driver
Statements
Expression rules
Success or failure
TERM
Consumes factors joined by multiplication or division.
EXP
Consumes terms joined by addition or subtraction.
Accepted language
A compact grammar for coursework
A program begins with program, an identifier, a variable
declaration, and begin. Its body can contain assignments,
read, write, and simple
for loops. The parser advances one lookahead token and
stops on the first rule that cannot be satisfied.
program → PROGRAM ID VAR idlist : INTEGER BEGIN statements END
idlist → ID { , ID }
assign → ID := expression
expr → term { ( + | - ) term }
term → factor { ( * | / ) factor }
factor → ID | INT | ( expression )Implementation
One source file per grammar routine
| File | Role |
|---|---|
main.c |
Reads tokens and validates the program level sequence and statements |
idlist.c |
Parses comma separated identifiers |
factor.c, term.c, exp.c
|
Apply arithmetic precedence |
assign.c, read.c |
Parse statement forms |
tokens.h |
Maps token names to the numeric input representation |
Result
The parser returns one binary result
The program prints success when the token stream matches
the expected grammar. Any mismatch follows the failure path, prints
failed, and returns a nonzero exit status.
make
./parser
# enter token numbers defined in tokens.hScope
This project implements syntax recognition only. Tokenization, source locations, recovery after an error, and an abstract syntax tree are outside its coursework scope.