ECMA-262

  by Dmitry Soshnikov

9 Comments:

1. scriptLover
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   10. August 2011 at 19:19
   

   very good initiative

   
   
2. Robert Polovsky
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   10. August 2011 at 23:03
   

   Thanks, Dmitry, it’s very interesting! Look forward to further explanations.

   
   
3. John Merge
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   11. August 2011 at 00:41
   

   Awesome!
   That will be definitely something huge!
   Thanks!

   
   
4. Mathias Bynens
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   11. August 2011 at 11:28
   

   My solution to homework assignment #2:

   var handle = {
   	'+': function(a, b) {
   		return a + b;
   	},
   	'-': function(a, b) {
   		return a - b;
   	},
   	'*': function(a, b) {
   		return a * b;
   	},
   	'/': function(a, b) {
   		return a / b;
   	},
   	'_default': function(a) {
   		return +a;
   	}
   };
   
   function evaluate(exp) {
   
   	var symbol = +exp;
   
   	if (exp == symbol) {
   		return symbol;
   	}
   
   	symbol = exp[0];
   	return (handle.hasOwnProperty(symbol) && handle[symbol] || handle._default)(evaluate(exp[1]), evaluate(exp[2]));
   
   }

   
   
5. Dmitry A. Soshnikov
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   11. August 2011 at 15:49
   

   @scriptLover, @Robert Polovsky, @John Merge, thanks, guys!

   @Mathias Bynens, yes, quite an elegant solution; very good.

   And by the way, the second lesson in a source code view is available!

   
   
6. Quildreen Motta
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   11. August 2011 at 21:00
   

   This be interesting. I love SICP, even though I haven’t worked out through all the exercises yet =/

   This is what I’ve come up with for lesson 1′s first two exercises:

   https://github.com/killdream/Essentials-of-interpretation/blob/master/solutions/lesson-1.js

   
   
7. Dmitry A. Soshnikov
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   11. August 2011 at 21:26
   

   @Quildreen Motta very good solution. I see you also implemented variables using environments — great, congrats! The next step is nested functions and scope chain lookups We will reach them in the next lessons.

   
   
8. Owen Densmore
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   11. September 2011 at 19:11
   

   I’ve been using Sage (sagemath.org) recently for linear algebra and other math work. Their notebooks are quite nice and provide a way for wonderful collaboration.

   BUT .. I realize Python is a lovely language but I’ve recently discovered how sophisticated JS is, and how complete it has made the JS world: node.js for servers, JS + HTML5 for clients, and JSON for communications between the two.

   So I’ve got two questions relating to your work:
   1 – How would I go about implementing operator overloading? It is a pretty important part of mathematics, I think, and keeps the notation uncluttered.
   2 – Could you point me to good existing mathematics in JS work?

   Thanks,

   — Owen

   
   
9. Dmitry A. Soshnikov
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   14. September 2011 at 20:25
   

   @Owen Densmore

   Sage seems a powerful framework for math (not sure how it correlates in tools with e.g. MatLab, but anyway, seems a good helper).

   Python is also very interesting language (actually, it has a similar semantics as JS: also completely dynamic, you may augment objects and classes at runtime, though, not built-in classes as in JS and Ruby).

   And about operator overloading, in the simplest way just comparing the types of operands. If they (or one of them) are strings, use concatenation, if operands are floats, use different algorithm, etc.

   Unfortunately I’m not aware about mathematics framework such as Sage in JS. But seems Python also fits nice

   This series though isn’t about mathematics much, but about interpretation of computer programs in general (though of course we touch some abstract data and operations, including primitive, such as math addition, etc, on them).

   
   

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