Associative array/Merging: Difference between revisions

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{color => yellow, name => Rocket Skates, price => 12.75}
{color => yellow, name => Rocket Skates, price => 12.75}
{color => red, price => 15.25, year => 1974}</pre>
{color => red, price => 15.25, year => 1974}</pre>

=={{header|PHP}}==
<lang php><?
$base = array("name" => "Rocket Skates", "price" => 12.75, "color" => "yellow");
$update = array("price" => 15.25, "color" => "red", "year" => 1974);

$result = $update + $base; // Notice that the order is reversed
print_r($result);
?></lang>
{{output}}
<pre>Array
(
[price] => 15.25
[color] => red
[year] => 1974
[name] => Rocket Skates
)</pre>

Alternative:
<lang php><?
$base = array("name" => "Rocket Skates", "price" => 12.75, "color" => "yellow");
$update = array("price" => 15.25, "color" => "red", "year" => 1974);

$result = array_merge($base, $update);
print_r($result);
?></lang>
{{output}}
<pre>Array
(
[name] => Rocket Skates
[price] => 15.25
[color] => red
[year] => 1974
)</pre>


=={{header|Python}}==
=={{header|Python}}==

Revision as of 08:58, 15 January 2020

Task
Associative array/Merging
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Define two associative arrays, where one represents the following "base" data:

Key Value
"name" "Rocket Skates"
"price" 12.75
"color" "yellow"

And the other represents "update" data:

Key Value
"price" 15.25
"color" "red"
"year" 1974

Merge these into a new associative array that contains every key found in either of the source ones. Each key should map to the value in the second (update) table if that exists, or else to the value in the first (base) table. If possible, do this in a way that does not mutate the original two associative arrays. Obviously this should be done in a way that would work for any data, not just the specific data given here, but in this example the result should be:

Key Value
"name" "Rocket Skates"
"price" 15.25
"color" "red"
"year" 1974

Factor

The assoc-union word does this. assoc-union! is a variant that mutates the first associative array.

Works with: Factor version 0.99 2019-10-06

<lang factor>USING: assocs prettyprint ;

{ { "name" "Rocket Skates" } { "price" 12.75 } { "color" "yellow" } } { { "price" 15.25 } { "color" "red" } { "year" 1974 } } assoc-union .</lang>

Output:
V{
    { "name" "Rocket Skates" }
    { "price" 15.25 }
    { "color" "red" }
    { "year" 1974 }
}

Go

<lang go>package main

import "fmt"

type assoc map[string]interface{}

func merge(base, update assoc) assoc { 

   result := make(assoc)
   for k, v := range base {
       result[k] = v
   }
   for k, v := range update {
       result[k] = v
   }
   return result

}

func main() { 

   base := assoc{"name": "Rocket Skates", "price": 12.75, "color": "yellow"}
   update := assoc{"price": 15.25, "color": "red", "year": 1974}
   result := merge(base, update)
   fmt.Println(result)

}</lang>

Output:
map[color:red name:Rocket Skates price:15.25 year:1974]

Haskell

There are various approaches, all of which would be strictly typed.
For example, if we want to treat the input and output records as all sharing the same type: <lang haskell>data Item = Item 

 { name :: Maybe String
 , price :: Maybe Float
 , color :: Maybe String
 , year :: Maybe Int
 } deriving (Show)

itemFromMerge :: Item -> Item -> Item itemFromMerge (Item n p c y) (Item n1 p1 c1 y1) = 

 Item (maybe n pure n1) (maybe p pure p1) (maybe c pure c1) (maybe y pure y1)

main :: IO () main = 

 print $
 itemFromMerge
   (Item (Just "Rocket Skates") (Just 12.75) (Just "yellow") Nothing)
   (Item Nothing (Just 15.25) (Just "red") (Just 1974))</lang>
Output:
Item {name = Just "Rocket Skates", price = Just 15.25, color = Just "red", year = Just 1974}

Java

<lang java>import java.util.*;

class MergeMaps { 

   public static void main(String[] args) {
       Map<String, Object> base = new HashMap<>();
       base.put("name", "Rocket Skates");
       base.put("price", 12.75);
       base.put("color", "yellow");
       Map<String, Object> update = new HashMap<>();
       update.put("price", 15.25);
       update.put("color", "red");
       update.put("year", 1974);

       Map<String, Object> result = new HashMap<>(base);
       result.putAll(update);

       System.out.println(result);
   }

}</lang>

Output:
{name=Rocket Skates, color=red, year=1974, price=15.25}

JavaScript

<lang javascript>(() => { 

   'use strict';

   console.log(JSON.stringify(
       Object.assign({}, // Fresh dictionary.
           { // Base.
               "name": "Rocket Skates",
               "price": 12.75,
               "color": "yellow"
           }, { // Update.
               "price": 15.25,
               "color": "red",
               "year": 1974
           }
       ), 
       null, 2
   ))

})();</lang>

Output:
{
  "name": "Rocket Skates",
  "price": 15.25,
  "color": "red",
  "year": 1974
}

Julia

julia> dict1 = Dict("name" => "Rocket Skates", "price" => 12.75, "color" => "yellow")
Dict{String,Any} with 3 entries:
  "name"  => "Rocket Skates"
  "price" => 12.75
  "color" => "yellow"

julia> dict2 = Dict("price" => 15.25, "color" => "red", "year" => 1974)
Dict{String,Any} with 3 entries:
  "price" => 15.25
  "year"  => 1974
  "color" => "red"

julia> merge(dict1, dict2)
Dict{String,Any} with 4 entries:
  "name"  => "Rocket Skates"
  "price" => 15.25
  "year"  => 1974
  "color" => "red"

julia> merge(dict2, dict1)
Dict{String,Any} with 4 entries:
  "name"  => "Rocket Skates"
  "price" => 12.75
  "year"  => 1974
  "color" => "yellow"

julia> union(dict1, dict2)
6-element Array{Pair{String,Any},1}:
  "name" => "Rocket Skates"
 "price" => 12.75
 "color" => "yellow"
 "price" => 15.25
  "year" => 1974
 "color" => "red"

Lua

<lang Lua>base = {name="Rocket Skates", price=12.75, color="yellow"} update = {price=15.25, color="red", year=1974}

--clone the base data -- result = {} for key,val in pairs(base) do 

   result[key] = val

end

--copy in the update data -- for key,val in pairs(update) do 

   result[key] = val

end

--print the result -- for key,val in pairs(result) do 

   print(string.format("%s: %s", key, val))

end</lang>

Output:
price: 15.25
color: red
year: 1974
name: Rocket Skates

MiniScript

MiniScript supports merging maps with the + operator. <lang MiniScript>base = {"name":"Rocket Skates", "price":12.75, "color":"yellow"} update = {"price":15.25, "color":"red", "year":1974}

result = base + update

print result</lang>

Output:
{"color": "red", "name": "Rocket Skates", "price": 15.25, "year": 1974}

Objective-C

Works with: Cocoa

<lang objc>#import <Foundation/Foundation.h>

int main(void) { 

 @autoreleasepool {
   NSDictionary *base = @{@"name": @"Rocket Skates", @"price": @12.75, @"color": @"yellow"};
   NSDictionary *update = @{@"price": @15.25, @"color": @"red", @"year": @1974};
   
   NSMutableDictionary *result = [[NSMutableDictionary alloc] initWithDictionary:base];
   [result addEntriesFromDictionary:update];
   
   NSLog(@"%@", result);
 }
 return 0;

}</lang>

Output:
{
    color = red;
    name = "Rocket Skates";
    price = "15.25";
    year = 1974;
}

Perl 6

Works with: Rakudo version 2019.11

I must say I somewhat disagree with the terminology. The requested operation is an update not a merge. Demonstrate both an update and a merge. Associative arrays are commonly called hashes in Perl 6.

<lang perl6># Show original hashes say my %base = :name('Rocket Skates'), :price<12.75>, :color<yellow>; say my %update = :price<15.25>, :color<red>, :year<1974>;

  1. Need to assign to anonymous hash to get the desired results and avoid mutating
  2. TIMTOWTDI

say "\nUpdate:\n", join "\n", sort %=%base, %update;

  1. Same

say "\nUpdate:\n", {%base, %update}.sort.join: "\n";

say "\nMerge:\n", join "\n", sort ((%=%base).push: %update)».join: ', ';

  1. Same

say "\nMerge:\n", ({%base}.push: %update)».join(', ').sort.join: "\n";

  1. Demonstrate unmutated hashes

say "\n", %base, "\n", %update;</lang>

Output:
{color => yellow, name => Rocket Skates, price => 12.75}
{color => red, price => 15.25, year => 1974}

Update:
color	red
name	Rocket Skates
price	15.25
year	1974

Update:
color	red
name	Rocket Skates
price	15.25
year	1974

Merge:
color	yellow, red
name	Rocket Skates
price	12.75, 15.25
year	1974

Merge:
color	yellow, red
name	Rocket Skates
price	12.75, 15.25
year	1974

{color => yellow, name => Rocket Skates, price => 12.75}
{color => red, price => 15.25, year => 1974}

PHP

<lang php><? $base = array("name" => "Rocket Skates", "price" => 12.75, "color" => "yellow"); $update = array("price" => 15.25, "color" => "red", "year" => 1974);

$result = $update + $base; // Notice that the order is reversed print_r($result); ?></lang>

Output:
Array
(
    [price] => 15.25
    [color] => red
    [year] => 1974
    [name] => Rocket Skates
)

Alternative: <lang php><? $base = array("name" => "Rocket Skates", "price" => 12.75, "color" => "yellow"); $update = array("price" => 15.25, "color" => "red", "year" => 1974);

$result = array_merge($base, $update); print_r($result); ?></lang>

Output:
Array
(
    [name] => Rocket Skates
    [price] => 15.25
    [color] => red
    [year] => 1974
)

Python

As of Python 3.5, this can be solved with the dictionary unpacking operator.

Works with: Python version 3.5+

<lang Python>base = {"name":"Rocket Skates", "price":12.75, "color":"yellow"} update = {"price":15.25, "color":"red", "year":1974}

result = {**base, **update}

print(result)</lang>

Output:
{'name': 'Rocket Skates', 'price': 15.25, 'color': 'red', 'year': 1974}

Alternative: <lang Python>base = {"name":"Rocket Skates", "price":12.75, "color":"yellow"} update = {"price":15.25, "color":"red", "year":1974}

result = dict(base) result.update(update)

print(result)</lang>

Output:
{'name': 'Rocket Skates', 'price': 15.25, 'color': 'red', 'year': 1974}

REXX

The REXX language has no native support to acquire the keys of an associate array after they have been defined,  
so it must be performed at definition time.

Some extra coding was added to support adjustable (maximum) widths for the displaying of the associate array names, keys, and values.

The double quotes that surround the string (character) items (as shown in the task's preamble) weren't included for this presentation. <lang rexx>/*REXX program merges two associative arrays (requiring an external list of indices). */ $.= /*define default value(s) for arrays. */ @.wAAn= 21; @.wKey= 7; @.wVal= 7 /*max widths of: AAname, keys, values.*/ call defAA 'base', "name Rocket Skates", 'price 12.75', "color yellow" call defAA 'update', "price 15.25", "color red", 'year 1974' call show 'base' call show 'update' call show 'new' exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ defAA: procedure expose $. @.; parse arg AAn; new= 'new' /*get AA name; set NEW.*/ 

        do j=2  to arg();   parse value arg(j)  with  key val   /*obtain key and value.*/
        $.AAn.key=val;                          /*assign a  value  to a  key for AAn.  */
        if wordpos(key, $.AAN.?keys)==0  then $.AAn.?keys=$.AAn.?keys key
                                                /* [↑]  add to key list if not in list.*/
        $.new.key=val                           /*assign a  value  to a  key for "new".*/
        if wordpos(key, $.new.?keys)==0  then $.new.?keys=$.new.?keys key
                                                /* [↑]  add to key list if not in list.*/
        @.wKey= max(@.wKey, length(key) )       /*find max width of a name of a  key.  */
        @.wVal= max(@.wVal, length(val) )       /*  "   "    "    " "   "   " "  value.*/
        @.wAA = max(@.wAAn, length(AAn) )       /*  "   "    "    " "   "   "    array.*/
        end   /*j*/
      return

/*──────────────────────────────────────────────────────────────────────────────────────*/ show: procedure expose $. @.; parse arg AAn; say; _= '═' /*set title char.*/ 

        do j=1  for words($.AAn.?keys)                                /*process keys.  */
        if j==1  then say  center('associate array', @.wAAn,     _)  ,
                           center("key"            , @.wKey,     _)  ,
                           center('value'          , @.wVal + 2, _)
        key= word($.AAn.?keys, j)                              /*get the name of a key.*/
        say center(AAn, @.wAAn)  right(key, @.wKey)  $.AAn.key /*show some information.*/
        end   /*j*/
      return</lang>
output   when using the internal default inputs:
═══associate array═══ ══key══ ═════value═════
        base             name Rocket Skates
        base            price 12.75
        base            color yellow

═══associate array═══ ══key══ ═════value═════
       update           price 15.25
       update           color red
       update            year 1974

═══associate array═══ ══key══ ═════value═════
         new             name Rocket Skates
         new            price 15.25
         new            color red
         new             year 1974

zkl

<lang zkl>base:=Dictionary( 

  "name", 	"Rocket Skates",
  "price", 	12.75,
  "color", 	"yellow",);

update:=Dictionary( 

  "price", 	15.25,
  "color", 	"red",
  "year", 	1974,);

update.pump( new:=base.copy() );

new.pump(Void,fcn([(k,v)]){ println("%s\t%s".fmt(k,v)) });</lang>

Output:
price	15.25
color	red
year	1974
name	Rocket Skates
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