Re: Delphi can do map/reduce?

Dan Downs escribió:
I don't think Delphi can't, I know I can pass a function but I don't understand this concept enough to solve it myself...

I can think of a couple ways to go about it, but I'm not sure its as eligant as functional languages.

The only real limitation I see is having to hard set your function types and parameter lists and matching your map functions to those so everything matches up correctly. There's a couple ways I can think of to make it a more flexible and dynamic, but I'm not sure its worth the added complexity and unless you were scaling it out to several cpus/systems the extra overhead would probably limit any gain.

If I converted the sample code correctly I think you'd end up with something like the following in delphi.

type
TMapableIntFunc = function( a, b : Integer) : Integer;
TMapableIntFunc = function( a, b : String) : String;

TIntegerArray = array of Integer;
TStringArray = array of String;

function IntReduce(fn : TMapableIntFunc; a : TIntegerArray; init : Integer) : Integer;
var
s, i : Integer;
begin
s := init;
for i := 0 to Length(a)-1 do
s := fn( s, a[i] );
Result := s;
end;

function sumInts(a : TIntegerArray) : Integer;
begin
Result := IntReduce( SumIntFunc, a, 0 );
end;

function StrReduce(fn : TMapableStrFunc; a : TStringArray; init : String) : String;
var
i : Integer;
s : String;
begin
s := init;
for i := 0 to Length(a)-1 do
s := fn( s, a[i] );
Result := s;
end;

function joinStrings(a : TStringArray) : String;
begin
Result := StrReduce( JoinStrFunc, a, "" );
end;

function SumIntFunc(a, b : Integer) : Integer;
begin
Result := a + b;
end;

function JoinStrFunc(a, b : String) : String;
begin
Result := a + b;
end;


By itself this doesn't really do much, but rewritting the IntReduce and StrReduce function to a multithreaded or message disbatching to server farm approach, would make this alot more interesting.

DD



Thanks to both...

Now I have a starting pont...

Also, other thing I think is embed python and do the map/reduce function on this and passing to delphi???

In the other side, what things are best/cool to have using this?
.

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