Transform LOOP0 language to Python code and execute it.

loop0_to.py

import re


class Loop0Transformer:
    rules = {
        r'(?P<indent>\s*)(?P<var1>\w+)\s*=\s*0': '{indent}{var1} = 0\n',  # v = 0
        r'(?P<indent>\s*)(?P<var1>\w+)\s*=\s*(?P<var2>\w+)\s*\+\s*1': '{indent}{var1} = {var2} + 1\n',  # v = w + 1
        r'(?P<indent>\s*)loop\s+(?P<var>\w+)(\s+begin)*': '{indent}for _ in range({var}):\n',  # loop v begin a
        r'(?P<indent>\s*)end': '{indent}# end for\n'  # This "transformation" is not really needed results in a comment
    }

    def __init__(self, loop_code: str):
        """
        Constructs the incomplete but sufficient minimal LOOP0 to Python translator.

        :param loop_code: The LOOP0 code *must* be indented accordingly,
                          because indentations will be retained for the sake of simplicity.
        """
        self._py_code = Loop0Transformer.transform(loop_code)
        print("-----------------\n"
              "Transformed code:\n"
              "-----------------\n", self._py_code, sep='')

    @staticmethod
    def transform(loop0_code: str):
        py_code = ''
        for (idx, line) in enumerate([line.rstrip() for line in loop0_code.splitlines() if line.strip() != '']):
            found_line_match = False
            for (rule, transformation) in Loop0Transformer.rules.items():
                match = re.match(rule, line, re.IGNORECASE | re.ASCII)
                if match:
                    py_code += transformation.format(**match.groupdict())
                    found_line_match = True
                    break
            if not found_line_match:
                print('[WARNING] Ignoring line (#{no}): "{content}"'.format(no=idx, content=line))
        return py_code

    def exec(self, initial_variables: {}):
        exec(self._py_code, {}, initial_variables)
        initial_variables.pop('_', None)
        return initial_variables


transformer = Loop0Transformer("""F(X1, X2) = X1 * X2 = Y:
Y = 0;
loop X1 begin
    loop X2 begin
        Y = Y + 1
    end
end
""")
print("=> Results: ", transformer.exec({'X1': 4, 'X2': 20}), '\n')

transformer = Loop0Transformer("""F(X1) = 2 ** X1 = Y:
Y = 0;
Y = Y + 1;
loop X1 begin
    loop Y begin    }
        Y = Y + 1   }-> Y = Y + Y <=> Y = Y * 2
    end             }
end 
""")
print("=> Results: ", transformer.exec({'X1': 10}), '\n')