Why MIT switched from Scheme to Python

Post by danbmil99 » Sun, Mar 29, 2009, 6:28 AM UTC

palish wrote: post #118

danbmil99 wrote: post #110

Earlier quoted context omitted.

"You also might have better luck running dynamics simulations with PhysX than with ODE." I worked on the simulator at Anybots, and I'm pretty much convinced a different physics engine isn't going to magically make things better (in terms of using simulations to predict real robot behavior). The problem is more about getting every little physical detail of the actual robot -- and its interactions with the environment…

Yeah, after giving it some thought, it would be very tough to repurpose a realtime physics simulator like PhysX or ODE to be useful to Anybots. But that doesn't necessarily mean that it isn't practical to create a simulator suited for rapid prototyping of robots. (I'm just brainstorming ideas in the rest of this post; I'm not sure whether they'll work, but it's a fun problem to think about.) Perhaps it would be usefu…

Post by danbmil99 » Sun, Mar 29, 2009, 6:43 AM UTC

asciilifeform wrote: post #131

danbmil99 wrote: post #129

Earlier quoted context omitted.

I believe I categorically disagree with every point you make. You are pissing in the wind if you think you can treat a system with 100M LOC the same way you wrote assembly on a 6502. They are different beasts, with totally different emergent properties. It's like claiming that you can understand the weather if you just stick to thinking about individual molecules. [edit:] I believe the xkcd strip can be read two ways…

> you are pissing in the wind if you think you can treat a system with 100M LOC the same way you wrote assembly on a 6502 I would be, if I actually believed that it is possible given current technology. However, I believe that the problem is technological rather than fundamental, and that we can arrive at a solution. Let me give you an example of a problem that was once thought to be fundamental and inescapable yet c…

Post by danbmil99 » Sun, Mar 29, 2009, 7:46 PM UTC

asciilifeform wrote: post #135

danbmil99 wrote: post #134

Earlier quoted context omitted.

I think we're talking past each other, though there is still a fundamental disagreement in principle. Of course I believe that science 'works', in the sense that in theory, everything should be reducible to a lower level description. High-level source code reduces to machine code; weather reduces to quantum mechanics. However, there's a critical decision about what level you choose to work at when you attack a proble…

I don't disagree with the necessity for fundamental elements ("black boxes") on top of which to build. My only complaint is with the universally shoddy state of these black boxes. Specifically: http://www.loper-os.org/?p=37 The modern computer is the first time mankind has built a system which is actually capable of perfection. You are more likely to have a spontaneous heart attack and die at any given moment than th…

Post by danbmil99 » Tue, Mar 31, 2009, 8:18 AM UTC

asciilifeform wrote: post #137

danbmil99 wrote: post #136

Earlier quoted context omitted.

we don't need lisp to know the state of the machine -- in the Linux case, we have source code. We can _theoretically_ debug everyone else's code and know exactly what is going on. "It is theoretically possible for the entire stack to work exactly as expected, and for each element to seem as inevitable and obvious-in-retrospect as Maxwell's equations." Yes, and it is theoretically possible according to the laws of phy…

Have you ever actually used a Lisp Machine? There is an emulator available (ask around.) All of these things were actually possible there - not merely theoretically.

Post by sadfsa » Sun, May 03, 2009, 11:05 PM UTC

mattjones wrote: post #45

tlb wrote: post #19

Earlier quoted context omitted.

I think here, "practicality" means "has a library for controlling robots". Also a good numeric library, a good matlab-like graphing library, good 3D graphics, good real-time performance, easy C++ embedding, etc. Rather than complaining about how everyone else is a bonehead for not using Lisp, write some libraries to make it useful for more things in the real world. Also, Python does pretty well for real-time control.…

Libraries aren't the issue. I use Chicken Scheme for a few things, which has plenty of libraries and a fantastic package system called eggs. Sure, other languages like Perl and Python have more libraries now, but that's not what made them popular. What made them popular was the design of the core languages. I started using Ruby because it was faster to type and easier to remember how to do things than Perl, not becau…

  (require scheme/foreign)
  (unsafe!)
  (define my-c-lib (ffi-lib "libmylib")) ;; loads libmylib.so
  (define my-c-func (get-ffi-obj 'my_c_func my-c-lib (_fun _long -> _long)))
  ;; The C code does not need to take Scheme into account--
  ;; Existing C libraries can be interfaced with Scheme
  ;; with a trivial amount of effort.

  #include 
  #include 
    
  static PyObject *
  py_htonl(PyObject *self, PyObject *args) {
     long my_arg;
 
     if(!PyArgParseTuple(args, "l", &my_arg))
         return NULL;
     return PyBuildValue("l", htonl(my_arg));
  }
  
  static PyMethodDef methods[] = {
      {"htonl", py_htonl, METH_VARARGS,
       "Demonstrate Python's C interface\n"}
  };
  
  static char module_doc[] = "Demonstration";  
  
  PyMODINIT_FUNC
  initfunc(void) {
    PyInitModule3("mylib", methods, module_doc);
  }