The goal of this project is to create an application for executing programs written in PL/0.
program
= block ".";
block
= ["const" identifier "=" number {"," identifier "=" number} ";"]
["var" identifier {"," identifier} ";"]
{"procedure" identifier ";" block ";" } statement
;
statement
=
[ identifier ":=" expression
| "call" expression
| "?" identifier
| "!" expression
| "begin" statement {";" statement} "end"
| "if" condition "then" statement
| "while" condition "do" statement
];
condition
= "odd" expression
| expression ("="|"#"|"<"|"<="|">"|">=") expression
;
expression
= ["+"|"-"] term {("+"|"-") term}
;
term
= factor {("*"|"/") factor}
;
factor
= identifier
| number
| "(" expression ")"
;
number
= ?[0-9]+?
;
identifier
= ?[A-Za-z_][A-Za-z0-9_]*?
;In practice, the keywords are often case-insensitive. Sometimes the identifiers are too. This implementation only treats the keywords as case-insensitive.
- Implement better parser error handling.
- Implement a general mechanism for logging diagnostic messages.
- Handle semantic analysis and symbol table creation before evaluation-time.
- Write unit tests for everything.
- Add command line options for fine-tuning how code will be compiled and executed.
- Make compiling dev features such as unit tests and the benchmark application optional in the build scripts.
- Add sections to this README about writing PL/0 programs.
- Write backend components consisting of the following:
- Semantic analyzer
- Optimizer
- Bytecode generator
- Virtual machine
Ultimately, I'd like to compile PL/0 code to a custom bytecode. The bytecode would then be executed by a simple virtual machine implementation (i.e. not a JIT).