Numarray question

[Robert Kern]

Matt Feinstein wrote:
> If I try
> 
> 
>>>>2 < array([1,2,3])
> 
> 
> I get:
> 
> array([0, 0, 1], type=Bool)
> 
> which is pretty slick, However if I set
> 
> 
>>>>q = 2 < array([1,2,3])
>>>>q and q
> 
> 
> I get a runtime error: "An array doesn't make sense as a truth value."
> 
> So..  why not? It seems to me that if I could vectorize logical
> expressions (a la Matlab), it would be a lot easier to write functions
> that will take either scalar or vector input values. Am I missing
> something?

logical_and(), logical_or(), etc. These will handle arrays of truth 
values rather than treating the array as a single truth value like "and" 
and "or" will do. The reason why the latter is left undefined is because 
there isn't much solid agreement about what the semantics should be. In 
the face of ambiguity, numarray refuses the temptation to guess and 
forces the user to explicitly request certain behavior via alltrue() or 
sometrue() or whatever strikes their fancy.

-- 
Robert Kern
rkern at ucsd.edu

"In the fields of hell where the grass grows high
  Are the graves of dreams allowed to die."
   -- Richard Harter