SamReidHughes 5 years ago

It fails to compile the program

    #include <iostream>

    int main() {
        int x = 23;
        std::cout << x;
        return 0;
    }
It seems like it can't handle namespaces.

When I write

    #include <vector>
it complains, "cannot find library: vector".

I think this isn't going to be very useful for people unless you get a C++ evaluator that works correctly. There is a demo of Clang running in the browser using webassembly here: >> https://tbfleming.github.io/cib/ << but it doesn't actually work for me on Firefox. Maybe I need to use Chrome. That is probably a better option for getting C++ running in the browser.

  • goalexboxer 5 years ago

    The repo of the original interpreter: https://github.com/felixhao28/JSCPP

    Which notable features are not implemented yet?

        Goto statements
        Object-oriented features
        Namespaces
        Multiple files support
    
    The target audience would consists in students trying simple algorithms. By the end of the high school, students are only using very basic C-syntax: variables, arrays, functions, and a couple of functions from the standard library.

    Some partial implementations: iostream (only cin and cout and endl) cmath cctype cstring cstdio (partial) cstdlib (partial)

    Other includes could be added too.

    What I am trying to highlight is if there is any possibility to increase the visual feedback for students heading first to programming.

    Something more like an interpretor would be more suitable in this case, but the wasm compilation doesn't seem too slow though. Thanks for this demo!

    • leetcrew 5 years ago

      > By the end of the high school, students are only using very basic C-syntax: variables, arrays, functions, and a couple of functions from the standard library.

      if the goal is to have them writing C-style C++ code, why not just use C? or if the goal is to teach C++, why start with only the features available in C?

      I've been a TA for classes in both C and C++, and I think we ultimately do a disservice to these students by not treating these languages more separately.

      • goalexboxer 5 years ago

        I agree. However, the goal of the computer science classes is to teach basic algorithms and data structures, and not focusing on the language particularly. For instance, in the national exam (written) you may use any printing function (printf / cout), but you are limited to use C-style string functions. No vectors, no additional containers C++. Pointers are being studied too, but there are no exercises which involve coding in exams for memory allocations, so you never get to choose between new/malloc. I don't like this situation but this is the problem I am trying to address, any idea is well appreciated!

    • SamReidHughes 5 years ago

      As far as I can tell, this interpreter doesn't even have std::string, and you can't define your own datatypes or allocate. The interpreter also doesn't handle pointers into arrays properly.

      I'm not familiar with other countries' curricula, but we had vectors and strings very early on when I learned C++. I like the general idea of the debugging interface, that could help a lot of people. But I think you should upgrade the interpreter. I don't know if that's possible while retaining the debugging interface, unfortunately.

      • goalexboxer 5 years ago

        These are the main downsides indeed. As a matter of fact, in the current curricula the only option is cstring, and it's been that way in the last 20 years. I am looking forward to put in balance the upsides and downsides in using such an interpreter. Thank you for feedback!

    • userbinator 5 years ago

      If it has no object-oriented features, then I don't think it deserves to be called a C++ interpreter at all, since that's basically the one feature everyone thinks of when they're asked to compare C and C++; from the description it looks more like a C-subset interpreter.

      • goalexboxer 5 years ago

        From the point of end user yes, but the original JSCPP project allows custom classes and members to be available via include.

ryanianian 5 years ago

Kinda neat but it looks extremely limited in ways that I think would frustrate a beginner:

E.g. the following doesn't do anything

  #include <iostream>
  using namespace std;
  int get7() { return 7; }
  int main() { return get7(); }
but if you manually inline the get7() it displays 7, so returning the value from another function doesn't work which seems quite odd and I think would preclude playing with recursion. (You can assign the get7() return value to a local var and return that and it works so there is a workaround but it's awkward.)

Similarly, if there are compiler errors it gives no indication as to what the error might be. C++ compiler errors are always pretty terrible but not showing anything about where even a parse went wrong could really get in the way of fixing typos etc that can really get in the way of learning the concepts.

  • goalexboxer 5 years ago

    In this case there are no variables updated so the editor is not very useful indeed. The parsing erros for this interpreter are very limited, however there is internal access to the location of the failure (line, column) so there could be added a red underline to suggest the errors. Thanks for the feedback!

goalexboxer 5 years ago

Hello,

I was thinking at a solution to teach code easier for the beginners. C++ is the only available language for computer science classes in my country.

The project is aimed to teach coding for students as the next step after Scratch.

The language implementation is just a subset of C++, it relies on JSCPP interpreter.

I am looking for feedback and suggestions.

Thanks!

  • hultner 5 years ago

    I’m curious as to which country it is that only teaches C++ for all programming?

    And why that is, sounds very particular. I started programming in C and C++. Back then it was the knly languages I could find books for in the library and I had managed to get my hands on a Borland compiler via an older cousin, but I wouldn’t have picked it as a newcomer language today.

    • goalexboxer 5 years ago

      In Romania. There are computer science classes starting 11 years old students in every school but Pascal and C/C++ are the only options.

  • pletnes 5 years ago

    What about jupyter and root instead? https://root.cern.ch/notebooks/HowTos/HowTo_ROOT-Notebooks.h...

    AFAIK it uses clang for parsing, which is as good a C++ parser as any.

  • davidcollantes 5 years ago

    It is completely broken (interface) on mobile.

    • goalexboxer 5 years ago

      At this point, sadly yes. I'm just experimenting to see if the live visualization is useful.

zach43 5 years ago

This is the definitely the best implementation of a C++ code visualization i've seen yet, kudos to the developers for this

That said, its a bit sad that this is in C++, which I think is an atrocious language for coding beginners to learn. Sure, a lot of people here might have learned C++ to start with (me included), but there are much, much better alternatives available today (pretty much any modern interpreted language for example).

I've noticed that people who are new to coding get the biggest boost to learn more about programming if they are in an environment where they can cause some kind of interesting visual output. In this regard, many languages that have good visual tooling integration (like Javascript's integration with HTML, python integrating with a GUI toolkit like pygame) really kicks it out of the park when it comes to motivating newcomers.

If the devs are reading this, could I suggest adding a 2D graphical component to this tool? unfortunately I can't think of any good, easy-to-use graphics APIs in C++ (a la the canvas API in JavaScript), but SFML and CairoMM come to mind.

svat 5 years ago

Good work, pleasing UI (when it works). Please also compare with the excellent pythontutor.com website (it works with C++ too: http://pythontutor.com/cpp.html ).

Examples of differences I can see:

* pythontutor requires a backend and does not run entirely in the browser.

* pythontutor supports much more of C++ (i.e., has fewer limitations)

* shows pointers, heap and stack better.

But there are probably many more differences; would like to see a comparison among similar resources. Anyway, I think this sort of live visualization is indeed very useful; great work and please continue.

  • goalexboxer 5 years ago

    Python Tututor is the first project in this category that I totally loved it. The dream would be to have all the options Python Tutor has and also speed and user experience, but technically there is not very easy to achieve. Thanks for the feedback!

zyngaro 5 years ago

Very Nice ! But it should be stated that this is not C++ but just C++ syntax.

lasagnaphil 5 years ago

This code, which is clearly undefined behavior (because of dangling pointer), outputs the number 2, which is very worrisome.

    #include <iostream>
    using namespace std;
    
    int* foo() {
        int y = 2;
        return &y;
    }
    int main() {
        int* x = foo();
        cout << *x << endl;
        return 0;
    }
I would recommend not using this for educational purposes yet; it could mislead students about pointer usage.
  • goalexboxer 5 years ago

    Fair point, I will definetly try to use a different compiler next time. Thanks for pointing this out!

turrini 5 years ago

If you create a variable as int and later change it to unsigned long long, it doesn't work anymore.

  • goalexboxer 5 years ago

    Yes, indeed. The live panel displays only basic types (long, char, int, floats and basic arrays). Thanks for noticing!

    • turrini 5 years ago

      Great idea and implementation, btw!

aboutruby 5 years ago

Great idea. For some reason it kept removing my semicolon after I used the time-traveling.

  • goalexboxer 5 years ago

    I haven't noticed that, could you please describe more your context, including the browser version and OS? Thank you!