Peano Arithmetic

Jason Orendorff jason.orendorff at gmail.com
Fri Aug 15 09:25:21 PDT 2008


On Fri, Aug 15, 2008 at 12:22 AM, Michael Haufe <TNO at thenewobjective.com> wrote:
> I apologize if this issue was discussed already, I've been unable to
> find an answer after a few hours of digging and Googling.
>
> I was watching some old SICP videos and translating some of the code
> into JavaScript to see how it compared to Scheme and came across a
> couple of errors when implementing Peano Arithmetic.

I think it's a case of mistranslation.  When Scheme says (+ x 1), the
right ECMAScript translation is x + 1, not x++.  So, in your examples:

>   return add2(x--,y++); //recursion error
return add2(x - 1, y + 1);

>   return add3(x,y)++; //error: cannot assign to a function result
return add3(x, y) + 1;

Incidentally, ECMAScript does not have Scheme-like tail recursion, so
the examples from SICP will not all necessarily work.

-j



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