[Haskell-beginners] Selecting Arguments in Function to Feed Map
Tommy M. McGuire
mcguire at crsr.net
Mon Sep 13 11:33:50 EDT 2010
And to finish the example, fully parenthesized:
Prelude> let x = 4
Prelude> let y = [1,2,3,4]
Prelude> let z = 3
Prelude> map ((flip (f x)) z) y
[7,11,15,19]
I.e., apply f to x, flip the arguments, apply z, and map the result across y.
On 09/13/2010 09:01 AM, Alex Rozenshteyn wrote:
> To actually give the example:
>
>> -- assuming that x and z are defined, and ys is the list
>> map (\y -> f x y z) ys
>
> On Mon, Sep 13, 2010 at 9:16 AM, Magnus Therning <magnus at therning.org
> <mailto:magnus at therning.org>> wrote:
>
> On Mon, Sep 13, 2010 at 14:03, Lorenzo Isella
> <lorenzo.isella at gmail.com <mailto:lorenzo.isella at gmail.com>> wrote:
> > Dear All,
> > Suppose you have the function
> >
> > f x y z = x*y +z
> >
> > and that you want to iterate it on a list
> > z=[1,2,3,4], with
> > x=4 and y=3
> >
> > then you would do the following
> >
> > map (f x y) z.
> >
> > Now consider the case in which the list is given by y e.g.
> >
> > y=[1,2,3,4], with
> > x=4 and z=3.
> >
> > How can you iterate f on y (i.e. its second argument) while
> keeping x and y
> > fixed?
>
> Using a lambda expression (anonymous function) or through clever use
> of flip.
>
> /M
>
> --
> Magnus Therning (OpenPGP: 0xAB4DFBA4)
> magnus＠therning．org Jabber: magnus＠therning．org
> http://therning.org/magnus identi.ca
> <http://identi.ca>|twitter: magthe
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> --
> Alex R
>
>
>
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Tommy M. McGuire
mcguire at crsr.net
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