• Bruno Medeiros (8/8) Jul 31 2010 Consider the familiar functional idiom "map"
• Dmitry Olshansky (9/15) Jul 31 2010 Generally ? transform, mutate. But most of the time you better get some
• Philippe Sigaud (29/35) Aug 01 2010 What parameter?
• Bruno Medeiros (14/23) Aug 03 2010 Partial-application/currying is another issue (related or not), but I
• Kagamin (2/5) Aug 01 2010 transform

Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:

Consider the familiar functional idiom "map" 
(http://en.wikipedia.org/wiki/Map_%28higher-order_function%29)

What would you call such a function parameter (either for map or just 
generally). That is, what would you call a function that takes one 
parameter of some type, and produces another object/data from that input?
Is there any usual name/term for this, I wonder, or not really?

-- 
Bruno Medeiros - Software Engineer

Dmitry Olshansky <dmitry.olsh gmail.com> writes:

On 31.07.2010 22:07, Bruno Medeiros wrote:
 Consider the familiar functional idiom "map" 
 (http://en.wikipedia.org/wiki/Map_%28higher-order_function%29)

 What would you call such a function parameter (either for map or just 
 generally). That is, what would you call a function that takes one 
 parameter of some type, and produces another object/data from that input?

Generally ? transform, mutate. But most of the time you better get some 
natural name close to semantics of operation (in any special cases).
 Is there any usual name/term for this, I wonder, or not really?

Well usually it's called map. And, in fact, there is very generic (and 
cute) one in Phobos by the very same name.
Sadly it's somewhat bogus right now (which is known compiler fault). 
There are some workarounds posted on NG.

-- 
Dmitry Olshansky

Philippe Sigaud <philippe.sigaud gmail.com> writes:

On Sat, Jul 31, 2010 at 20:07, Bruno Medeiros
<brunodomedeiros+spam com.gmail> wrote:

 Consider the familiar functional idiom "map" (
 http://en.wikipedia.org/wiki/Map_%28higher-order_function%29)

 What would you call such a function parameter (either for map or just
 generally).


What parameter?



 That is, what would you call a function that takes one parameter of some
 type, and produces another object/data from that input?

Do you mean the partial application of map, is in D with map!"a*a" ?
(without any argument).


Is there any usual name/term for this, I wonder, or not really?

Not sure if I'm saying something obvious to you, but map is a higher-order
function: a function that acts on functions, either taking them as
parameter(s) or as results. So are filter, fold/reduce, unfold, scan,
compose, power (of a function: power(f, n) = f(f(f(... n times)))
For map, filter or reduce, the function is just a parameter among two. Most
of the time, what they create is not a function.

In curried language like Haskell, you can easily create the partial
application of a function: n-args functions are in fact n 1-arg functions
each delivering the next step (a function).
So map x*x [0,1,2,3,4] is [0,1,4,9,16], but map x*x is a function, waiting
for an iterable and returning its transformation through x*x. In not-curried
language, map x*x is considered a partial application of map.

Note in D the asymmetry between the function which is a compile-time
argument and the range, a runtime argument. A recent change in Phobos (for
the next release) by Andrei will allow us to do:

alias map!"a*a" squarer; // squarer is a _generic_ function taking any
range, as long as the operation a*a makes sense for the range elements.


Before, we could do this with reduce, but not map and filter. That was
originally to avoid a bug in the compiler :-) but it's easy to code and very
useful.

We could have a map(fun, range) in D, I guess. Gone the currying, but
welcome runtime functions.

Philippe

Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:

Partial-application/currying is another issue (related or not), but I 
made no mention of it.
I meant map simply as "higher-order function that applies a given 
function element-wise to a list of elements and returns a list of 
results". No currying involved.

On 01/08/2010 09:34, Philippe Sigaud wrote:
 On Sat, Jul 31, 2010 at 20:07, Bruno Medeiros
 <brunodomedeiros+spam com.gmail> wrote:

     Consider the familiar functional idiom "map"
     (http://en.wikipedia.org/wiki/Map_%28higher-order_function%29)

     What would you call such a function parameter (either for map or
     just generally).


 What parameter?

According to what I said above, the parameter that is a function (the 
function that will transform the elements). The only other parameter is 
the collection or iterator.


     That is, what would you call a function that takes one parameter of
     some type, and produces another object/data from that input?

I meant generally. So for example if you were coding in Java or some 
other language that does not have first order functions, but instead 
have to wrap them as an interface, what would you call the interface?


-- 
Bruno Medeiros - Software Engineer

Kagamin <spam here.lot> writes:

Bruno Medeiros Wrote:

 What would you call such a function parameter (either for map or just 
 generally). That is, what would you call a function that takes one 
 parameter of some type, and produces another object/data from that input?

transform