• Dfr (4/4) Dec 24 2013 Let's say i have array of kind:
• Gary Willoughby (4/8) Dec 24 2013 You can if the initial array was comprised of tuples instead of
• Philippe Sigaud (8/12) Dec 24 2013 To build a value (your b) from a range (a), you can use
• bearophile (7/13) Dec 24 2013 While this code seems correct (and I think it's kind of common in
• Philippe Sigaud (12/22) Dec 24 2013 I don't know Scala much (I find the code it makes me write is far too
• monarch_dodra (8/13) Dec 24 2013 you use map and filter to reduce a structure down to a value? Or
• Philippe Sigaud (3/8) Dec 24 2013 Something I use often. Same here, btw: everyday, there are posts code
• Timon Gehr (8/12) Dec 24 2013 void main(){
• Dfr (4/21) Dec 25 2013 This example looks cleanest, but not compile with error:
• bearophile (4/7) Dec 25 2013 It compiles for me.
• Dfr (2/10) Dec 25 2013 Sorry, just forgot to import "std.array", now it works, thank you.

"Dfr" <deflexor yandex.ru> writes:

Let's say i have array of kind:

auto a = [["1","0000FF"], ["2", "00FF00"], ...];

Is there simple way to turn it into associative array of kind:

string[string] b = ["1": "0000FF", "2": "00FF00", ...];

"Gary Willoughby" <dev nomad.so> writes:

On Tuesday, 24 December 2013 at 11:36:23 UTC, Dfr wrote:
 Let's say i have array of kind:

 auto a = [["1","0000FF"], ["2", "00FF00"], ...];

 Is there simple way to turn it into associative array of kind:

 string[string] b = ["1": "0000FF", "2": "00FF00", ...];

You can if the initial array was comprised of tuples instead of 
nested arrays.

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

On Tue, Dec 24, 2013 at 12:36 PM, Dfr <deflexor yandex.ru> wrote:
 Let's say i have array of kind:

 auto a = [["1","0000FF"], ["2", "00FF00"], ...];

 Is there simple way to turn it into associative array of kind:

 string[string] b = ["1": "0000FF", "2": "00FF00", ...];

To build a value (your b) from a range (a), you can use
std.algorithm.reduce, it's a very generic algo:


    auto a = [["1","0000FF"], ["2", "00FF00"]];
    import std.algorithm: reduce;
   string[string] b;
    b = reduce!((aa, pair) { aa[pair[0]] = pair[1]; return aa;})(b,a);
    writeln(b);

"bearophile" <bearophileHUGS lycos.com> writes:

Philippe Sigaud:

     auto a = [["1","0000FF"], ["2", "00FF00"]];
     import std.algorithm: reduce;
    string[string] b;
     b = reduce!((aa, pair) { aa[pair[0]] = pair[1]; return 
 aa;})(b,a);
     writeln(b);

While this code seems correct (and I think it's kind of common in 
Scala), I consider it an obfuscation to avoid. A normal foreach 
loop is much more readable and should be preferred for this. 
Functional-style programming is not always the best.

Bye,
bearophile

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

On Tue, Dec 24, 2013 at 1:12 PM, bearophile <bearophileHUGS lycos.com> wrote:
 Philippe Sigaud:


     auto a = [["1","0000FF"], ["2", "00FF00"]];
     import std.algorithm: reduce;
    string[string] b;
     b = reduce!((aa, pair) { aa[pair[0]] = pair[1]; return aa;})(b,a);
     writeln(b);


 While this code seems correct (and I think it's kind of common in Scala)

I don't know Scala much (I find the code it makes me write is far too
'heavy', if I may say so).
Haskell would be more the origin of my using reduce :-)

 consider it an obfuscation to avoid. A normal foreach loop is much more
 readable and should be preferred for this. Functional-style programming is
 not always the best.

I don't know. I really consider `reduce` a nice way to collapse a
structure down to a value. I find it in many different places. Sure,
map and filter are more usual, but reduce is not far behind.

Anyway... Here with a foreach loop:

    auto a = [["1","0000FF"], ["2", "00FF00"]];
    string[string] b;

    foreach(pair; a)
        b[pair[0]] = pair[1];

"monarch_dodra" <monarchdodra gmail.com> writes:

On Tuesday, 24 December 2013 at 12:33:13 UTC, Philippe Sigaud 
wrote:
 I don't know. I really consider `reduce` a nice way to collapse 
 a
 structure down to a value. I find it in many different places. 
 Sure,
 map and filter are more usual, but reduce is not far behind.

you use map and filter to reduce a structure down to a value? Or 
do you mean it's just something you use often?

I don't think map+filter can be used to "reduce" a range down to 
a value. It would require a filter with mutable state, and I'm 
pretty sure doing that means having an implementation defined 
result.

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

On Tue, Dec 24, 2013 at 3:07 PM, monarch_dodra <monarchdodra gmail.com> wrote:
 I don't know. I really consider `reduce` a nice way to collapse a
 structure down to a value. I find it in many different places. Sure,
 map and filter are more usual, but reduce is not far behind.


 you use map and filter to reduce a structure down to a value? Or do you mean
 it's just something you use often?

Something I use often. Same here, btw: everyday, there are posts code
with map in it.

Timon Gehr <timon.gehr gmx.ch> writes:

On 12/24/2013 12:36 PM, Dfr wrote:
 Let's say i have array of kind:

 auto a = [["1","0000FF"], ["2", "00FF00"], ...];

 Is there simple way to turn it into associative array of kind:

 string[string] b = ["1": "0000FF", "2": "00FF00", ...];

void main(){
     import std.array, std.algorithm, std.typecons;
     auto a = [["1","0000FF"], ["2", "00FF00"], /+...+/];
     auto aa = a.map!(x=>tuple(x[0],x[1])).assocArray;

     import std.stdio;
     writeln(aa);
}

"Dfr" <deflexor yandex.ru> writes:

On Tuesday, 24 December 2013 at 14:39:16 UTC, Timon Gehr wrote:
 On 12/24/2013 12:36 PM, Dfr wrote:
 Let's say i have array of kind:

 auto a = [["1","0000FF"], ["2", "00FF00"], ...];

 Is there simple way to turn it into associative array of kind:

 string[string] b = ["1": "0000FF", "2": "00FF00", ...];

 void main(){
     import std.array, std.algorithm, std.typecons;
     auto a = [["1","0000FF"], ["2", "00FF00"], /+...+/];
     auto aa = a.map!(x=>tuple(x[0],x[1])).assocArray;

     import std.stdio;
     writeln(aa);
 }

This example looks cleanest, but not compile with error:

Error: no property 'assocArray' for type 'MapResult!(__lambda9, 
immutable(char[][])[])'

"bearophile" <bearophileHUGS lycos.com> writes:

Dfr:

 This example looks cleanest, but not compile with error:

 Error: no property 'assocArray' for type 'MapResult!(__lambda9, 
 immutable(char[][])[])'

It compiles for me.

Bye,
bearophile

"Dfr" <deflexor yandex.ru> writes:

On Wednesday, 25 December 2013 at 14:44:57 UTC, bearophile wrote:
 Dfr:

 This example looks cleanest, but not compile with error:

 Error: no property 'assocArray' for type 
 'MapResult!(__lambda9, immutable(char[][])[])'

 It compiles for me.

 Bye,
 bearophile


Sorry, just forgot to import "std.array", now it works, thank you.