Add runner portion of the interpreter

The interpreter is now complete. Apart from bugs that may be hiding in the code, it should work now.

lambdaV.py

@@ -75,6 +75,19 @@ def draw_field():
         print("")
 
 
+# returns "" or error message
+# Parsed code is the result of running the parser,
+# though at this point the input is assumed to be valid
+# and no additional checks are performed on what the parser produced.
+def run_code(parsed_code):
+    for i in range(len(parsed_code[0])):
+        result = parsed_code[0][i](*parsed_code[1][i])
+        if not result=="":
+            return result
+        draw_field()
+    return ""
+
+
 def condition_facing_north(inverted):
     if inverted:
         return not cursor_current == cursor_north
@@ -449,10 +462,19 @@ def parse_code(code, allowed_commands, allowed_conditions, unformatted_code=True
                 return [[], [], parse_position, "Syntax error: Unknown control structure: "+control_structure, code]
     return parsed_code
 
+# A wrapper for run_code that deals with potential errors produced by the parser.
 # returns success or error message
-# Parsed code is the result of running the parser.
+def evaluate_parser_result(parsed_code):
-def run_code(parsed_code):
+    if not parsed_code[2]==-1:
-    return ""
+        # parser error
+        return parsed_code[3] + "\n" + (" "*parsed_code[2]) + "↓\n" + parsed_code[4]
+    outcome = run_code(parsed_code)
+    if not outcome=="":
+        # runtime error
+        # TODO: pass back information about where the error occurred
+        return outcome
+    #TODO: check if goal reached
+    return "Success!"
 
 if __name__ == "__main__":
     pass