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June 25, 2014 / cdsmith

Big changes coming to CodeWorld

I’m continuing work on CodeWorld, my educational programming environment based on geometry and algebra.  There are big changes coming!  If you’re interested in following the project, please join the new codeworld-discuss mailing list, where I’ll send more regular announcements about significant changes, as well as try to answer questions, and discuss future directions.

Here are some things I intend to change in the near future.  A more complete list is on the project issue tracker, but this is a summary with more details and reasoning about some of the changes.

Aligning With Math Education

An important goal of this project is to align with a standards-based U.S. middle school math education, as much as possible.  To be clear, I still refuse to add complexity or turn the project into a patchwork of specific lessons that promote a specific narrow path of learning.  First and foremost, this should be an environment for tinkering and encountering ideas in self-motivated way.  But given alternative designs that could each be valid on their own, I’ll choose the one that pushes students toward the math standards.

It’s sometimes a tough line to draw.  But I’ve become convinced that there are a few places where I can do better.  Two of those are going to be major breaking changes, coming soon.

1. Death to Currying

Haskell’s convention of currying functions is the wrong default for CodeWorld.  Practically all of mathematics, especially at introductory level, is carried out with the notation f(x,y) = … .  The interpretation is that a function of two parameters is a function whose domain is a product – a set of ordered pairs.  The Haskell language makes a different choice.  Applying a function to two parameters is more like f(x)(y) (the parentheses are optional in Haskell itself), and the interpretation is that f(x) denotes a partially applied function that’s still waiting for its second parameter.

If the goal were to teach about higher-order functions, there would be lots of great arguments for the latter.  If the goal were convenience, you could argue for the latter pretty persuasively, as well.  I think Haskell’s use of currying is great.  But when the goal is to let students encounter and tinker with things they will see in school math, the right choice is to adopt the convention of mathematics.

Luckily, the assumption of curried multi-parameter functions isn’t baked into Haskell too deeply.  By changing the standard library, it’s quite possible to write f(x,y) just as well.  The parentheses on f(x) become optional, but this is actually true of mathematics in general (for example, operators in linear algebra are often written without parentheses, as are trig functions).  I will adopt the convention of using parentheses around even single function parameters.

The only big source of awkwardness comes with binary operators.  So long as we choose not to teach the notations `foo` (for turning a function into an operator) or (+) (for turning an operator into a function), this doesn’t come up much.  Notably, sections still work fine, since they take only one argument.

A couple convenient side effects of this choice are nice, too:

  • Students who routinely write parentheses around function arguments less often find themselves forced to surround negative numbers in parentheses for weird parsing reasons.  As trivial as it might seem, this was a very real and significant learning obstacle the last time I taught the class, and I’ll be happy to see it go.
  • Getting expression structure wrong sometimes gives much better error messages this way.  It’s harder to accidentally mix up precedence between an operator and function application; and passing too few arguments to a function gives a clear error rather than inferring a function type and breaking in an obscure way elsewhere.

2. Resizing the Canvas

The second big change is to resize the canvas from 500×500 to 20×20.

The justification for a 500×500 canvas was generally about confusing pixels – little dots on the screen – with the general idea of a coordinate system.  It’s convenient to blur the distinction at first, but it has in the past become a barrier to understanding the full nature of the coordinate plane with real (or even rational) coordinates.  Many students were confused when later faced with fractional coordinates.  At the same time, developing a full understanding of the rational number system is a big topic in 6th, 7th, and 8th grade mathematics, so it would be great to ask students to do more tinkering with these numbers.

By replacing this with a 20×20 grid (x and y coordinates ranging from -10 to 10), several goals are accomplished:

  • Students early in the class are working with numbers in a range they can comprehend better.
  • Students routinely work in fractions or decimals to fine tune their projects.
  • The abstract coordinate plane, including fractional coordinates, becomes more familiar.

This is a big win overall.

Changes to Usability

On the less controversial side, I’m planning a number of changes to make the site more usable:

  • Pervasive auto-complete, based on a pre-populated list of the standard library symbols as well as parsing the student code for declared names.
  • More complete documentation, tutorials, and better examples.  I admit that the current site is grossly lacking in documentation.  I don’t envy anyone who tries to figure it out on their own!
  • Better tools for playing around with results.  At the very least, students will be given the chance to scroll, pan, and see coordinates of points in pictures, animations, and simulations.

Long-Term Wish List

I also have my wish list for things I’d love to see possible, but am not quite ready to build yet.  This includes:

  • Social features: sharing projects with friends, commenting on or expressing support for other projects.
  • Collaborative projects with shared editing or exporting libraries for others to use.
  • Better debugging tools, such as easy controls to move forward and back in time, fast-forward, pause, etc. for animations, simulations, and even games.
  • Possibly grading features for teachers to grade projects and provide a scoring rubric and comments.

What else would you like to see?  Let me know in the comments here, on codeworld-discuss, or by filing a feature request in the issue tracker.

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