Search a list of records: Difference between revisions

{{out}}

<pre>

6

Khartoum-Omdurman

4.58

</pre>

=={{header|C sharp|C#}}==

<lang csharp>using System;

using System.Collections.Generic;

namespace RosettaSearchListofRecords

{

class Program

{

static void Main(string[] args)

{

var dataset = new List<Dictionary<string, object>>() {

new Dictionary<string, object> {{ "name" , "Lagos"}, {"population", 21.0 }},

new Dictionary<string, object> {{ "name" , "Cairo"}, {"population", 15.2 }},

new Dictionary<string, object> {{ "name" , "Kinshasa-Brazzaville"}, {"population", 11.3 }},

new Dictionary<string, object> {{ "name" , "Greater Johannesburg"}, {"population", 7.55 }},

new Dictionary<string, object> {{ "name" , "Mogadishu"}, {"population", 5.85 }},

new Dictionary<string, object> {{ "name" , "Khartoum-Omdurman"}, {"population", 4.98 }},

new Dictionary<string, object> {{ "name" , "Dar Es Salaam"}, {"population", 4.7 }},

new Dictionary<string, object> {{ "name" , "Alexandria"}, {"population", 4.58 }},

new Dictionary<string, object> {{ "name" , "Abidjan"}, {"population", 4.4 }},

new Dictionary<string, object> {{ "name" , "Casablanca"}, {"population", 3.98 }}

};

// Find the (zero-based) index of the first city in the list whose name is "Dar Es Salaam"

var index = dataset.FindIndex(x => ((string)x["name"]) == "Dar Es Salaam");

Console.WriteLine(index);

// Find the name of the first city in this list whose population is less than 5 million

var name = (string)dataset.Find(x => (double)x["population"] < 5.0)["name"];

Console.WriteLine(name);

// Find the population of the first city in this list whose name starts with the letter "A"

var aNamePopulation = (double)dataset.Find(x => ((string)x["name"]).StartsWith("A"))["population"];

Console.WriteLine(aNamePopulation);

}

}

}</lang>

=={{header|Perl 6}}==

The built-in method <tt>.first</tt> fulfills the requirements of this task.<br>

It takes any [https://docs.perl6.org/language/operators#infix_~~ smart-matcher] as a predicate. The <tt>:k</tt> adverb makes it return the key (i.e. numerical index) instead of the value of the element.

{{Works with|Rakudo|2016.08}}

<lang perl6>my @cities =

{ name => 'Lagos', population => 21.0 },

{ name => 'Cairo', population => 15.2 },

{ name => 'Kinshasa-Brazzaville', population => 11.3 },

{ name => 'Greater Johannesburg', population => 7.55 },

{ name => 'Mogadishu', population => 5.85 },

{ name => 'Khartoum-Omdurman', population => 4.98 },

{ name => 'Dar Es Salaam', population => 4.7 },

{ name => 'Alexandria', population => 4.58 },

{ name => 'Abidjan', population => 4.4 },

{ name => 'Casablanca', population => 3.98 },

;

say @cities.first(*<name> eq 'Dar Es Salaam', :k);

say @cities.first(*<population> < 5).<name>;

say @cities.first(*<name>.match: /^A/).<population>;</lang>

{{out}}

<pre>

6

Khartoum-Omdurman

4.58

</pre>