Can call functions and print text.

interpreter.py

@@ -28,6 +28,7 @@ class Interpreter():
     def __init__(self, code):
         self.ast = parser.build_ast(code)
         self.sanity_check_ast()
+        self.project = None
         
     def sanity_check_ast(self):
         if not isinstance(self.ast, nodes.CodeBlock):
@@ -37,8 +38,42 @@ class Interpreter():
         first = self.ast.get_statements()[0]
         if not isinstance(first, nodes.FunctionCall) or first.get_function_name() != 'project':
             raise InvalidCode('First statement must be a call to project')
-            
+    
+    def run(self):
+        i = 0
+        statements = self.ast.get_statements()
+        while i < len(statements):
+            cur = statements[i]
+            if isinstance(cur, nodes.FunctionCall):
+                self.function_call(cur)
+            else:
+                print("Unknown statement in line %d." % cur.lineno())
+            i += 1
+
+    def function_call(self, node):
+        func_name = node.get_function_name()
+        if func_name == 'project':
+            args = node.arguments.arguments
+            if len(args) != 1:
+                raise InvalidCode('Project() must have one and only one argument.')
+            if not isinstance(args[0], nodes.StringStatement):
+                raise InvalidCode('Project() argument must be a string.')
+            if self.project is not None:
+                raise InvalidCode('Second call to project() on line %d.' % node.lineno())
+            self.project = args[0].get_string()
+            print("Project name is %s." % self.project)
+        elif func_name == 'message':
+            args = node.arguments.arguments
+            if len(args) != 1:
+                raise InvalidCode('Message() must have only one argument')
+            if not isinstance(args[0], nodes.StringStatement):
+                raise InvalidCode('Argument to Message() must be a string')
+            print('Message: %s' % args[0].get_string())
 
 if __name__ == '__main__':
-    code = "project('myawesomeproject')"
+    code = """project('myawesomeproject')
+    message('I can haz text printed out?')
+    message('It workses!')
+    """
     i = Interpreter(code)
+    i.run()

nodes.py

@@ -48,6 +48,9 @@ class StringStatement(Statement):
         assert(type(value) == type(''))
         Statement.__init__(self, lineno)
         self.value = value
+        
+    def get_string(self):
+        return self.value
 
 class FunctionCall(Statement):
     def __init__(self, func_name, arguments, lineno):
@@ -90,6 +93,9 @@ class Arguments(Statement):
     def prepend(self, statement):
         self.arguments = [statement] + self.arguments
 
+    def __len__(self):
+        return len(self.arguments)
+
 def statement_from_expression(expr):
     if isinstance(expr, AtomExpression):
         return AtomStatement(expr.value, expr.lineno())

parser.py

@@ -150,8 +150,7 @@ def test_parser():
     print(build_ast(code))
 
 def build_ast(code):
-    if not code.endswith('\n'):
-        code = code + '\n'
+    code = code.rstrip() + '\n'
     lex.lex()
     parser = yacc.yacc()
     result = parser.parse(code)