Py-PL0-Interpreter

A PL/0 Interpreter implemented in Python

Grammar

The grammar is based on wikipedia's PL/0 page.

program = block "." ;

block = [ "const" ident "=" number {"," ident "=" number} ";"]
        [ "var" ident {"," ident} ";"]
        { "procedure" ident ";" block ";" } statement ;

statement = [ ident ":=" expression | "call" ident 
              | "?" ident | "!" 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 = ident | number | "(" expression ")";

Keywords

Note: Keywords are case-insensitive in this implementation.

const: declares constants
var: declares variables
procedure: declares a procedure
call: calls a procedure
begin: composite statements
end: composite statements ends
if: conditional statement condition
then: conditional statement body
while: loop statement condition
do: loop statement body
odd: condition operator, returns true if the expression is odd

Operators

+, -: unary operators
+, -, *, /: arithmetic operators
=, #, <, <=, >, >=: comparison operators
:=: assignment operator
?: input operator
!: output operator
;: statement separator
,: variable separator
(, ): parenthesis
.: program end

Features

Lexer: converts source code into tokens
Parser: converts tokens into an AST
ASTInterpreter: interprets the AST
IR Generator: generates an IR from the AST
IR Interpreter: interprets the IR

Use the Interpreter

TODO

Test

To test a certain program, either use pytest to run the test file (not covering a lot) or run the following command:

python3.11 <path-to-program> <path-to-input>

and the output will be printed to the console.

Dorapower / Py-PL0-Interpreter