Need help in understanding a python code

Steven D'Aprano steve at REMOVE-THIS-cybersource.com.au
Sun Nov 16 11:31:16 CET 2008


On Sun, 16 Nov 2008 01:50:16 -0800, John Machin wrote:

> > def A(w, v, i,j):
> >     if i == 0 or j == 0: return 0
> >     if w[i-1] > j:  return A(w, v, i-1, j)
> >     if w[i-1] <= j: return max(A(w,v, i-1, j), v[i-1] + 
> >       A(w,v, i-1, j - w[i-1]))


>> I am reading this blog
>>
>> http://20bits.com/articles/introduction-to-dynamic-programming/
> 
> I suggest that you don't bother reading a blog written by somebody who
> (presumably consciously) keyed in that "if w[i-1] <= j: " above.

That is a translation of standard terminology for a hybrid function. 
Mathematics doesn't have an "else", so you write hybrid functions by 
enumerating each branch as an if.

While it's not especially good Python technique, it's a perfectly 
idiomatic mathematical expression, and shouldn't be the basis for 
dismissing an entire blog.


-- 
Steven



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