Context-free grammar for VBA

Question

I'm trying to scan and parse VBA (visual basic for application) code for a school assignment.

I'm using Python PLY lex and yacc modules. Right now I'm just trying to get variable declaration and assignments to work as a proof of concept. My preliminary grammar understands a variable declaration OR an assignment. As soon as I put a newline (\\n) character in there and add another statement it doesn't understand anything. ie: In the code in the gist, if you remove "a = 3" from the string at line 92, it will work fine, and insert an Identifier in the identifier list.

I handle newline characters in the scanner, so I think there's something wrong with my grammar definition, but can't figure it out.

The grammar is basically this:

statement : declaration
          | assignment

declaration : DIM IDENTIFIER AS TYPE

assignment : IDENTIFIER ASSIGN BOOLEAN
           | IDENTIFIER ASSIGN DOUBLE
           | IDENTIFIER ASSIGN INT

Note that IDENTIFIER, ASSIGN, BOOLEAN, DOUBLE, INT DIM, AS and TYPE are all tokens defined in the lex module.

I've created a gist with the code which is at: https://gist.github.com/clsk/22c386695dd1ddb7ca75

Answer 1

@rici wrote:

That's a grammar for a single statement. Why do you expect it to work with multiple statements? Nowhere is there a production which indicate that multiple statements are legal input.

The OP wrote:

Indeed that was the issue. Thanks for the pointer