Learning goals

You will learn or practice how to:

1. Work with binary search trees as part of a larger program.
2. Refactor existing code, avoiding breaking previous tests.
3. Submit code that is has finished some functionality.

Overview

In this homework, you will adapt your code from HW15 to allow parsing JSON objects. At this point, you will have the majority of the functionality of a JSON parser working. Refer to the previous parts for specifications on valid and invalid JSON.

This assignment serves two purposes:

1. Adds the major missing functionality to your JSON parser. This project might be good for a resume.
2. For those who did not finish preious JSON homeworks, this is one last chance to submit JSON for credit.

A JSON file contains text that represents a number, a string, a list, an object, a boolean, or null. Here are some examples:

type	json	data
number	10	10
string	"ten"	"ten"
list	[2, 6, 4]
list	{"key1": "value", "key2" true}	Imagine a lovely picture of a binary search tree here. There is an image from lecture on 8/2, you can find it on the schedule page.
boolean	true	true
null	null

Linked lists

As in C, whitespace is ignored (except within a string). Lists and objects can both contain any type of data, thus all the following are valid:

type	json	data
list	[2, 6, 4]
list	[2, 6, "four"]
list	[2, [3, "+", 3], "four"]

Getting Started on EC04

1. The starter code for EC04 is the same as previous JSON assignment. You will be required to modify the header to add the new functions.
2. Start by creating a directory and cp to copy your code from HW15.
e 264get EC04 to fetch the starter code.
you@ecegrid-thin1 ~/ $ cd 264
you@ecegrid-thin1 ~/264/ $ mkdir ec04
you@ecegrid-thin1 ~/264/ $ cp hw15/* -v -t ec04/
you@ecegrid-thin1 ~/264/ $ cd ec04
you@ecegrid-thin1 ~/264/ec04 $
3. Start by fixing functionality from previous JSON parts that you did not finish in time for HW15. The majority of the credit for ec04 will be fore previous functonality.
4. Make a submission. You will get credit for ec04 as long as you have more functionality finished than on HW15.
5. Let me reiterate, finish previous functionality first before you worry about objects. You do not have to be finished to make a submission, as long as it compiles and passes some of your tests and it
6. Start by creating a helper to insert key and an element into a binary search tree. Recommended signature: void _bst_insert(BSTNode** a_root, char const* key, Element element).
7. We recommend finishing get_element(…) next. You can test it by creating binary trees manually using your helper function.
8. Test and submit.
9. Next, update print_element(…) to support objects. This will help you debug.
10. Test and submit.
11. Create parse_object(…)
1. Start by implementing code to parse an empty object.
2. Test and submit.
3. Next, create code to parse an element with a single key and value.
4. Test and submit.
5. Next, update the code to parse two key and value pairs.
6. Test and submit.
7. Update the code to parse any number of key and value pairs.
8. Test and submit.
9. Finally, add code to handle any invalid cases you did not handle before.
10. Test and submit.
12. Update parse_element(…) to support JSON objects.
13. Create recursive helper function to free the binary search tree. Recommended signature: void _free_tree(BSTNode** a_root).
14. Finally, update free_element(…) to support JSON objects.
15. Test that there are no memory leaks, even for incorrect input.

Requirements

Submit

To submit EC04 from within your ec04 directory, type 264submit EC04 json.c json.h test_json.c miniunit.h clog.h Makefile *.json

If your code does not depend on miniunit.h or clog.h, those may be omitted. Your json.h will most likely be identical to the starter. Makefile will not be checked, but including it may help in case we need to do any troubleshooting. Make sure to submit all required json files required by your tests. It is your responsibility to ensure the tester has all the files required to test. You are encouraged to modify your Makefile to do so.

Pre-tester ●

The pre-tester for EC04 has been released and is ready to use.

Q&A

1. How can I structure my tests?

   Here's a start. (We may add to this at some point.)

   // OK TO COPY / ADAPT this snippet---but ONLY if you understand it completely.
   // ⚠ Do not copy blindly.
   // 
   // This test is nowhere near adequate on its own.  It is provided to illustrate how to
   // use helper functions to streamline your test code.
   
   #include <stdio.h>
   #include <stdlib.h>
   #include "json.h"
   #include "miniunit.h"
   
   // helper headers you wish to use from json.h
   void _bst_insert(BSTNode** a_root, char* key, Element element);
   
   // all tests from JSON 4, do not delete old tests!!!
   
   static int _test_parse_object_two_values() {
     mu_start();
     //──────────────────────────────────────────────────────
   
     char const* input = "{\"key1\": 123, \"key2\": \"value\"}ABC";
     char const* pos = input;
     BSTNode* root;
     bool is_success = parse_object(&root, &pos);
     mu_check(is_success);   // because the input is valid
     // I was too lazy to count the characters, so made C count it for me
     // the 3 is the trailing characters
     mu_check(pos == input + strlen(input) - 3); 
     mu_check(root != NULL);
     // we could check specific locations in the tree,
     // or we could just use the helper which does not care
     Element* a_element = get_element(root, "key1");
     mu_check(a_element != NULL);
     mu_check(a_element->type == ELEMENT_INT);
     mu_check(a_element->as_int == 123);
     element = get_element(root, "key2");
     mu_check(a_element != NULL);
     mu_check(a_element->type == ELEMENT_STRING);
     mu_check_strings_equal(a_element->as_string, "value");
   
     free_element((Element){.as_object = root, .type = ELEMENT_OBJECT});
     //──────────────────────────────────────────────────────
     mu_end();
   }
   
   int main(int argc, char* argv[]) {
     mu_run(_test_parse_object_two_values);
     mu_run(_test_write_int_zero);
     return EXIT_SUCCESS;
   }
   

2. That string looks super messy, is there a nicer way we can write it?

   You may find it easier to create JSON objects as files. This will prevent the need to escape all the double quotes. You could create helper functions to make your tests easier to write. Some examples are below, Example JSON object file contents:

         {
           "key1": "This is a string",
           "key2": 12345,
           "nested_object": {
               "with a nested list": [ 1, 2, true, null ],
               "okay, this object is probably a bit complex": true,
               "you probably want to test simplier ones :)": false
           }
         }
       

3. I finished HW15, can I submit this homework without doing objects?

   The requirement for this assigmnent is you must have more functionality working than you had in the previous JSON homework. You do not need to finish all of objects to get some credit, just printing JSON objects would get you some credit.

4. Isn't this requirement unfair for those who finished HW15?

   Those who already finished HW15 already got credit for that code. That said, if you did well on the previous parts you should have no trouble handling objects here.

5. Can I turn in this assignment late?

   Due to how close we are to the end of the semester, late work is unlikely to be accepted. Submit early and often and follow TDD to ensure you get as much credit for your work as possible.

Updates

Updates will be posted here if any.