A fully functioning Quack compiler that generates assembly-like C code from a given Quack program.

Created by Andrew Letz and Natalie Letz.

At a few points in developing the compiler, a decision needed to be made regarding what is allowed in the language. This is a list of the decisions I made (almost all of them in the type checking phase).

• Method and class arguments are treated as explicit declarations
• You may not have a field with the same name as a class or method
• You may not have a method with the same name as a class
• You may not include an explicit "return" statement in a constructor
• You cannot pass "this" as an argument in a constructor (as the object may not be completely initialized yet)
• You cannot assign a variable to "this" in a class
• You may not use the keyword "this" inside of the main program statements
• You cannot use the dot operator (field access) on a builtin. eg, "z".foo or 2.bar
• Typecase variables that are introduced must not share a name with any existing variable in that scope
• Dots of form this.this are prohibited

• If the method in which an error occurs has the same name of the class it is in, that means it occurred in the constructor. eg, "invalid type assigned to variable x in method Classname() in class Classname()"
• If an error occurs in either the method or class $MAIN(), that means the error occurred in the main statements area.
• Some errors may be reported more than once in type checking/inference.

Type

./build.sh

to get the qcc executable.

*note: you may have to run the command chmod +x build.sh in order to run the script

Usage

./qcc [filename] [-json]\* [-verbose]\* [-debug]\* [-ast]\*

[-json] flag will print the program's abstract syntax tree in JSON format to stdout.

[-debug] flag will compile-stage start/completion messages.

[-ast] will skip the initialization before use and type checking stages, allowing you to generate the AST image for an invalid program.

[-verbose] will print program information such as the inferred types of variables and class information.

Type

./clean.sh

to get rid of the build directory and the qcc executable.

• good_simple_inherited_method_printing.qk -> shows off dynamic dispatch on executing an inherited method
• good_Pt.qk -> shows off dynamic dispatch on executing Obj's built-in PRINT with Pt's overriden STR
• good_simple_if_and_short_circuit.qk -> shows both if statements and short circuit evaluation
• good_typecase.qk -> shows off typecase working properly, works on all types of objects (obj, nothing, int, user-defined class)
• good_control_flow.qk -> shows off all types of control flow as well as printing based on execution path taken
• good_the_kitchen_sink -> shows off most things in the language, uncomment things to see some errors
• good_typewalk.qk -> shows off crawling up the class hierarchy to infer the right type for a method (abstract semantics)
• bad_typewalk.qk -> same principle as good_typewalk.qk, but with a small error at the top of the class hierarchy

Once you have have the compiled qcc binary, you can type

./generateast.sh [qcc executable] [filename]

to automatically generate the AST image for that file. Output file will be a .png with the same name as the .qk file.

*note: you must have json_to_dot.py in the same directory as the script.

*another note: you must have graphviz installed on your machine to use this script (gives access to the "dot" command).

This script was created by another student, Zayd Hammoudeh.

More information can be found on the repository managed by him and the professor Michal Young:

https://github.com/UO-cis561/quack-tests-static

Professor Michal Young for several helpful repos that can be found here:

https://github.com/UO-cis561