wkemery / cosc4785_program3

adding Bison functionality

COSC4785_Program3

Valid input: Currently the only standalone input that my program will accept is an expression or a variable declaration. All other parts of the grammar must be a smaller part of one of those.

A note: I did implement arglist before instructed not to and i chose to take it out. However, since it can be empty, it should create no problems with your testing.

Changes in the Grammar: The biggest change I made was in how a variable is declared. First off, I made a production called multibracks. it is used in the var declaration rules. When we have the full grammar, I plan to change it to be more consistent with the actual grammar.

How I print things out: Everything should be printing as described in the instructions except for some expressions. For example given 2+2. my program will print out --> --> 2 --> + --> 2

I did this because sum op could be a number of things and so I made it a node in my tree. Mine does not print: --> + --> 2 --> 2

Error handling: I added some basic error handling rules. Many of them are something along the lines, missing a right parenthesis or missing a semicolon. However, some account for errors in the middle of a production. For example, simpletype error SEMI this allows for some more detailed error messaged. I hope to expand these once we have the full grammar.

The biggest decision I made when choosing how to handle errors, is I chose, if given enough information to construct a node, I construct it, in it's entirety. However, I mark it as an error node and I mark all of its children as error nodes. This made continuing parsing a bit easier. And having more information about what the original input looked like seemed like a good idea to me. However, I currently do not print "dirty" error node trees, nor do I even add them to the final parse tree. However, this can be changed for needs in the future. ALso the memory of a bad node tree is freed before it is lost.