Simple Pascal Interpreter

This is a simple interpreter, which I have been writing in Java. It's based on a series ["Let's build a simple interpreter"] (https://ruslanspivak.com/lsbasi-part1/). The series is great. I highly recommend it to you.

For now, the interpreter supports following stuff:

• PROGRAM keyword;
• Block for declaration variables, which starts with VAR keyword;
• BEGIN ... END blocks;
• Integer variables like 'foo', 'bar' 'w42' and so on;
• Assignment operator ':=';
• Integer and real variables;
• binary operations: '+', '-', '*', 'div' and '/';
• unary operations: '+', '-';
• parenthesized expressions with arbitrary depth nesting.

Grammar

    program : PROGRAM variable SEMI block DOT

    block : declarations compoundStatement

    declarations : VAR (varsDeclaration SEMI)+
                 | empty

    varsDeclaration : ID (COMMA ID)* COLON typeSpec

    typeSpec : INTEGER | REAL

    compoundStatement : BEGIN statementList END

    statementList : statement
                  | statement SEMI statementList

    statement : compoundStatement
              | assignmentStatement
              | empty

    assignmentStatement : variable ASSIGN expr

    variable : ID

    empty :

    term ((PLUS | MINUS) term)*

    term : factor ((MUL | INTEGER_DIV | REAL_DIV) factor)*

    factor : INTEGER_CONST
           | REAL_CONST
           | PLUS factor
           | MINUS factor
           | LPAREN expr RPAREN
           | variable

How to use

> java -jar spi.jar test.pas