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Search a list of records: Difference between revisions
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The population of the first city in this list whose name starts with the letter "A": 4.58000
</pre>
=={{header|Ada}}==
This solution in inspired by how the <code>Ada.Containers</code> child packages work. Usually a <code>Cursor</code> contains two accesses: one to the container and one to the element. Since we want to get the index of the element as well, the index was stored instead.
{{works with|Ada|Ada|2005}}
<lang Ada>with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Text_IO;
procedure Search_A_List_Of_Records
is
function "+"(input : in String) return Unbounded_String renames To_Unbounded_String;
function "+"(input : in Unbounded_String) return String renames To_String;
type City is record
name : Unbounded_String;
population : Float;
end record;
type City_Array is array(Positive range <>) of City;
type City_Array_Access is access City_Array;
type Cursor is record
container : City_Array_Access;
index : Natural;
end record;
function Element(C : in Cursor) return City is
begin
if C.container = null or C.index = 0 then
raise Constraint_Error with "No element.";
end if;
return C.container.all(C.index);
end Element;
function Index_0(C : in Cursor) return Natural is
begin
if C.container = null or C.index = 0 then
raise Constraint_Error with "No element.";
end if;
return C.index - C.container.all'First;
end Index_0;
function Find
(container : in City_Array;
check : not null access function(Element : in City) return Boolean)
return Cursor
is
begin
for I in container'Range loop
if check.all(container(I)) then
return (new City_Array'(container), I);
end if;
end loop;
return (null, 0);
end;
function Dar_Es_Salaam(Element : in City) return Boolean is
begin
return Element.name = "Dar Es Salaam";
end Dar_Es_Salaam;
function Less_Than_Five_Million(Element : in City) return Boolean is
begin
return Element.population < 5.0;
end Less_Than_Five_Million;
function Starts_With_A(Item : in City) return Boolean is
begin
return Element(Item.name, 1) = 'A';
end Starts_With_A;
cities : constant City_Array :=
((+"Lagos", 21.0),
(+"Cairo", 15.2),
(+"Kinshasa-Brazzaville", 11.3),
(+"Greater Johannesburg", 7.55),
(+"Mogadishu", 5.85),
(+"Khartoum-Omdurman", 4.98),
(+"Dar Es Salaam", 4.7 ),
(+"Alexandria", 4.58),
(+"Abidjan", 4.4 ),
(+"Casablanca", 3.98));
begin
Ada.Text_IO.Put_Line(Index_0(Find(cities, Dar_Es_Salaam'Access))'Img);
Ada.Text_IO.Put_Line(+Element(Find(cities, Less_Than_Five_Million'Access)).name);
Ada.Text_IO.Put_Line(Element(Find(cities, Starts_With_A'Access)).population'Img);
end Search_A_List_Of_Records;</lang>
{{out}}
<pre> 6
Khartoum-Omdurman
4.58000E+00
</pre>
=={{header|ALGOL 68}}==
<lang algol68># Algol 68 doesn't have generic array searches but we can easily provide #
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