A simple Racket parser. It reads in source code, compares it to an internal grammar, and outputs either Accept or an error message.
One caveat is that the error messages are not as nice as I'd like. Ideally they would read something like Syntax error on line 5, but currently we're getting Encountered unexpected token of type 'MISC (value "*") while parsing 'unknown [line=5, column=#f, offset=73]. I probably need the srcloc function to get the output I want, but I haven't been able to get it working right.
- main.rkt - Main program. Contains the
parse()function. - grammar.rkt - Contains grammar notation for
#bragmodule. BNF-esque. - tokenizer.rkt - Tokenize input stream before passing to
grammar.rkt. - unit-tester.rkt - Allows easier testing of input files. Not used in final product.
I heavily consulted the Beautiful Racket tutorials for this assignment, especially the bf and jsonic exercises. Although I wrote my own code, there may be some structural similarities to these exercises.
My code relies on a couple of educational libraries that were developed for the Beautiful Racket book:
Finally, I frequently consulted the official Racket docs in developing this code.
| File | Oracle | Notes |
|---|---|---|
| input1.txt | Pass | A minimal program, but enough is there to be valid. |
| input2.txt | Pass | Not quite so minimal, but this should parse OK. Note that your program only needs to do parsing, not semantic analysis; your need not worry about undeclared or uninitialized variables. You are concerned only with the mechanical form of the code. |
| input3.txt | Fail | This has an error. The "then" will be interpreted as an identifier, and our grammar does not allow 2 identifiers in a row. |
| input4.txt | Pass | Binary v. unary minus. This should parse, as adding -273 to a variable should be legal. (The + begins the etail, the - is a numsign.) An additional operator would be illegal, of course. |
| input5.txt | Fail | Syntax error, illegal character ('*') in arithmetic expressions. |