symtab02.py

from spi import Lexer, Parser, NodeVisitor, BuiltinTypeSymbol, VarSymbol


class SymbolTable(object):
    def __init__(self):
        self._symbols = {}

    def __str__(self):
        symtab_header = 'Symbol table contents'
        lines = ['\n', symtab_header, '_' * len(symtab_header)]
        lines.extend(
            ('%7s: %r' % (key, value))
            for key, value in self._symbols.items()
        )
        lines.append('\n')
        s = '\n'.join(lines)
        return s

    __repr__ = __str__

    def insert(self, symbol):
        print('Insert: %s' % symbol.name)
        self._symbols[symbol.name] = symbol


class SemanticAnalyzer(NodeVisitor):
    def __init__(self):
        self.symtab = SymbolTable()

    def visit_Block(self, node):
        for declaration in node.declarations:
            self.visit(declaration)
        self.visit(node.compound_statement)

    def visit_Program(self, node):
        self.visit(node.block)

    def visit_Compound(self, node):
        for child in node.children:
            self.visit(child)

    def visit_NoOp(self, node):
        pass

    def visit_VarDecl(self, node):
        # For now, manually create a symbol for the INTEGER built-in type
        # and insert the type symbol in the symbol table.
        type_symbol = BuiltinTypeSymbol('INTEGER')
        self.symtab.insert(type_symbol)

        # We have all the information we need to create a variable symbol.
        # Create the symbol and insert it into the symbol table.
        var_name = node.var_node.value
        var_symbol = VarSymbol(var_name, type_symbol)
        self.symtab.insert(var_symbol)


if __name__ == '__main__':
    text = """
program SymTab2;
   var x, y : integer;

begin

end.
"""
    lexer = Lexer(text)
    parser = Parser(lexer)
    tree = parser.parse()

    semantic_analyzer = SemanticAnalyzer()
    semantic_analyzer.visit(tree)

    print(semantic_analyzer.symtab)