Hi Mike and Jason,
Thanks a lot for the quick response. My problem becomes a bit more
obvious if I have a function of several variables. Then the map
function becomes somehow impractical because I can't define which list
is used for which variable. List comprehensions also get a lot more
difficult. Example:
sage: var('a b c')
sage: f = a*x^2+b
sage: w = [4,5,6]
sage: z = [7,8,9]
sage: map(f,v,w,z)
[53, 133, 249]
sage: map(f,w,v,z)
[197, 322, 489]
I wouldn't even know how to do this with a list comprehension in one
step. Since the functions I work with have to be applied to time
series of quite a few variables, I am really desperate for a practical
way of doing this. So far, all mathematical programs I worked with
were able to do this and I bet that many people are used to applying
functions to lists and arrays. Isn't this a lot faster than defining
loops?
Stan
On Nov 19, 4:20 pm, Jason Grout <[EMAIL PROTECTED]> wrote:
> Mike Hansen wrote:
> > Hi Stan,
>
> > You should use Python's list comprehensions to do that:
>
> > sage: f = 2*x^3+1
> > sage: v = [1,2,3]
> > sage: [f(x=a) for a in v]
> > [3, 17, 55]
>
> > or you could do
>
> > sage: map(f, v)
> > [3, 17, 55]
>
> The question was: Is there an easy way of
> performing operations on arrays or lists without defining loops?
>
> The answer is: no, not really. Functions don't automatically thread
> themselves over lists. List comprehensions and maps provide a simple
> way to loop over a set, though.
>
> Personally, I think it's generally a good thing that functions don't
> automatically thread themselves over lists.
>
> Jason
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