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Why MIT switched from Scheme to Python

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Re: Why MIT switched from Scheme to Python

#51

Post by sharkbrainguy »

jules wrote: post #10
trjordan wrote: post #3

I think there's something else here, implicit in Sussman's comment, that's important. MIT was founded on a philosophy of practicality, and everything else is secondary. If you couple that with the belief that fundamental computer science is the most efficient way to enhance practical software engineering, Scheme was a wonderful choice. Java and C++ may have been more directly practical to software engineers, but they…

> If you can convey 95% of the basic ideas in Python But you cannot. Some of the ideas in SICP can nearly be conveyed in Python (like lexical scoping, closures, data types, streams). You'll use built-in language features in Python (classes, generators) instead of implementing the functionality. I think that implementing these things is important if you want to really understand them. An example, cons, car and cdr fro…

  def cons(a, b):
      return lambda f: f(a, b)

  def car(p):
      return p(lambda a,b: a)

  def cdr(p):
      return p(lambda a,b: b)
As well as in theory you can do this in practice. It's about as elegant (hard for me to judge as I have a strong pro-lisp bias).

Aside from lack of tail safety and performance issues with writing scheme-ish code I don't see why you couldn't implement those things in Python. The main difference is that typically in a real world situation you wouldn't because there's a library or a language feature

Re: Why MIT switched from Scheme to Python

#52

Post by tlb »

palish wrote: post #44
tlb wrote: post #41

Earlier quoted context omitted.

My point was there's no single 'gl.Vertex3' call that takes native Lisp numbers. Thinking about double/float/int/short should be abstracted out below the Lisp level. We use OpenGL to show real-time renderings of the robot, derived from the gyros and joint angle sensors. We have an analysis tool that shows, either in real time or post-run analysis, renderings synchronized with high-speed video of the robot and scrolli…

Ah. Very cool. Are you computing center of mass / moment of inertia yourself, or using a 3rd party library to do it? PhysX is free, and I believe it can do those calculations for you fairly automatically. (In PhysX, a 'scene' is composed of 'actors', and each actor is described by a set of shape descriptors. A shape descriptor can represent a box, a sphere, a capsule, a convex hull, etc. So a laptop actor could crude…

I use a very simple and exact O(N) algorithm to calculate mass properties of polyhedrons without computing convex hulls or anything:

http://www.cs.berkeley.edu/~jfc/mirtich/massProps.html

Maybe 80 LOC. I'm not sure why anything more complex is needed.

PhysX does seem promising.

Re: Why MIT switched from Scheme to Python

#53

Post by tlb »

acdha wrote: post #42
tlb wrote: post #33

Earlier quoted context omitted.

People often say that Java has great libraries, but is it true? AWT is crufty and ugly. Maybe there are impressive XML parsers (Xerxes is 188,000 lines of Java!), but I don't want those. Numerical libraries seem bad. So what is the library that might convince me to use Java for something?

"The" library is which ever squirrelly database, file format, app, etc. your next project needs to talk to which doesn't have bindings for your favorite language. You compromise on Java to avoid writing that by hand and use a JVM language to avoid the pain of actually using Java.

Such as??? Can anyone point to a format I might want to use that has a Java library but no C++ or Python library?

Re: Why MIT switched from Scheme to Python

#54

Post by sethg »

trjordan wrote: post #3

I think there's something else here, implicit in Sussman's comment, that's important. MIT was founded on a philosophy of practicality, and everything else is secondary. If you couple that with the belief that fundamental computer science is the most efficient way to enhance practical software engineering, Scheme was a wonderful choice. Java and C++ may have been more directly practical to software engineers, but they…

I'm wondering if pressure on MIT to develop demonstrable practical skills in underclassmen has increased since (classic) 6.001 was introduced. I mean, if you're smart enough to get into MIT in the first place and you learn Scheme as a sophomore and CLU as a junior, then by the time you graduate and look for a job, you should be able to get up to speed pretty quickly in Java or C++ or whatever the flavor of the month is. But if you're looking for work in the summer between your sophomore and junior year, the employers don't want you to spend two weeks out of a two-month internship learning the syntax of an industry-standard language.

Re: Why MIT switched from Scheme to Python

#55

Post by NonEUCitizen »

tlb wrote: post #33
time_management wrote: post #9

I wonder, if the switch had been made now, it they would have switched to Clojure instead of Python. It's a lot closer to Scheme, and its connection to the JVM gives it a lot of practical power. Does anyone have any thoughts on this?

People often say that Java has great libraries, but is it true? AWT is crufty and ugly. Maybe there are impressive XML parsers (Xerxes is 188,000 lines of Java!), but I don't want those. Numerical libraries seem bad. So what is the library that might convince me to use Java for something?

lucene

Re: Why MIT switched from Scheme to Python

#56

Post by drawkbox »

anthonyb wrote: post #39
tlb wrote: post #28

Earlier quoted context omitted.

Yes, I use PyOpenGL in GTK (with GTKGLExt). People have said good things about Gazebo, but I haven't used it. Most of the 3D stuff is performance-critical, so I typically prototype in Python and then convert to C++, which for graphics code isn't too painful. The Boost.Python interface makes it pretty easy. Also, the Cairo graphics interface is wonderful for drawing charts, animated robot stick figures, and many other…

For Python, there are also a number of game libraries around which you might be able to repurpose. Pyglet, Pygame and PyOgre are three which spring to mind. Depending on exactly what you're trying to do, of course...

Panda3D, developed by Disney and given to CMU for research. One real MMO built off of it, Pirates of the Caribbean.

Re: Why MIT switched from Scheme to Python

#57

Post by palish »

tlb wrote: post #52
palish wrote: post #44

Earlier quoted context omitted.

Ah. Very cool. Are you computing center of mass / moment of inertia yourself, or using a 3rd party library to do it? PhysX is free, and I believe it can do those calculations for you fairly automatically. (In PhysX, a 'scene' is composed of 'actors', and each actor is described by a set of shape descriptors. A shape descriptor can represent a box, a sphere, a capsule, a convex hull, etc. So a laptop actor could crude…

I use a very simple and exact O(N) algorithm to calculate mass properties of polyhedrons without computing convex hulls or anything: http://www.cs.berkeley.edu/~jfc/mirtich/massProps.html Maybe 80 LOC. I'm not sure why anything more complex is needed. PhysX does seem promising.

Yeah, that works. I mentioned computing convex hulls because I wasn't sure whether your CAD program exports "manifold" meshes, that is, closed polygonal meshes where each edge is connected to exactly two faces. When a mesh is manifold, it is possible to compute whether a point in space lies within or outside of the mesh, for example. It is also possible to compute the mesh's mass properties. In the video game industry, artists create models with techniques that are much less precise than CAD techniques, and so non-manifold meshes are very common, which makes them difficult to analyze in physical ways. The solution to that problem is to decompose the mesh into a set of convex hulls, then analyze the convex hulls.

The other reason I mentioned convex hull computation is because PhysX can only simulate dynamic actors that are composed of boxes, spheres, capsules, and convex hulls, IIRC. Arbitrary polygon meshes aren't supported for dynamic actors, because they are very difficult to simulate in realtime. So if you wanted to use PhysX for dynamics simulations, you would probably need to decompose your model into a set of convex hulls.

Good luck -- if you need any assistance with PhysX, feel free to contact me at shawnpresser@gmail.com.

Re: Why MIT switched from Scheme to Python

#58

Post by silentbicycle »

sharkbrainguy wrote: post #51
jules wrote: post #10

Earlier quoted context omitted.

> If you can convey 95% of the basic ideas in Python But you cannot. Some of the ideas in SICP can nearly be conveyed in Python (like lexical scoping, closures, data types, streams). You'll use built-in language features in Python (classes, generators) instead of implementing the functionality. I think that implementing these things is important if you want to really understand them. An example, cons, car and cdr fro…

def cons(a, b): return lambda f: f(a, b) def car(p): return p(lambda a,b: a) def cdr(p): return p(lambda a,b: b) As well as in theory you can do this in practice. It's about as elegant (hard for me to judge as I have a strong pro-lisp bias). Aside from lack of tail safety and performance issues with writing scheme-ish code I don't see why you couldn't implement those things in Python. The main difference is that typi…

It's also counterbalanced by there being an obviously standard, reasonably portable distribution of Python. You go to Python.org, and there it is.

It took me a while to find a Lisp that I liked, and it certainly wasn't a decision I was prepared to make while I was still trying to learn the basics. (I eventually settled on Chicken Scheme.)

Re: Why MIT switched from Scheme to Python

#59

Post by silentbicycle »

jerf wrote: post #49
silentbicycle wrote: post #38

Earlier quoted context omitted.

Python has some issues that can really interfere with doing Scheme-style FP in in it (no tail-call optimization, single-expression-only lambdas, closure/scope problems, general hostility from Guido), but IMHO it's a great general-purpose language, and well suited to teaching, particularly for introducing higher-order functions. Lua has much more Scheme influence than Python does (while being otherwise pretty similar)…

Yeah, that's why I called it "what they used to call functional programming". Functions are first-class values and closures are easy to get at. (Some people quibble with the exact implementation, but they are definitely there. Such people will be happier with Python 3.0, but still not entirely satisfied.) This is what "functional programming" used to mean. Now it means having immutable values, tail recursion, easy la…

Agreed. I originally said "lisp-style", but changed it to "scheme-style" for just that reason.

Re: Why MIT switched from Scheme to Python

#60

Post by mitko »

Hi, I am MIT student in CS and I took 6.001 (the new course is called 6.01). When I asked the instructor why we are using some language that has almost no practical use, they told me that the reasons are: - it teaches the concepts of the class well - after it one can learn any programming language very easily.

I believe both of these to be true. From my point of view the new 6.01 sacrifises depth for breadth. This is part of much bigger change of the ciriculum in MIT. That's why I hurried to take all nice classes before they get destroyed.

P.S. I didn't know python untill 2 weeks ago. But I learned in need very fast - definitely having background in different programming languages helps a lot.

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