Monads/List monad: Difference between revisions
Added Delphi example
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(bind vecstr)) ; also evaluates to ["6" "8" "10"]
</lang>
=={{header|Delphi}}==
{{libheader| System.SysUtils}}
{{Trans|Go}}
<lang Delphi>
program List_monad;
{$APPTYPE CONSOLE}
uses
System.SysUtils;
type
TmList = record
Value: TArray<Integer>;
function ToString: string;
function Bind(f: TFunc<TArray<Integer>, TmList>): TmList;
end;
function Create(aValue: TArray<Integer>): TmList;
begin
Result.Value := copy(aValue, 0, length(aValue));
end;
{ TmList }
function TmList.Bind(f: TFunc<TArray<Integer>, TmList>): TmList;
begin
Result := f(self.Value);
end;
function TmList.ToString: string;
var
i: Integer;
begin
Result := '[ ';
for i := 0 to length(value) - 1 do
begin
if i > 0 then
Result := Result + ', ';
Result := Result + value[i].toString;
end;
Result := Result + ']';
end;
function Increment(aValue: TArray<Integer>): TmList;
var
i: integer;
begin
SetLength(Result.Value, length(aValue));
for i := 0 to High(aValue) do
Result.Value[i] := aValue[i] + 1;
end;
function Double(aValue: TArray<Integer>): TmList;
var
i: integer;
begin
SetLength(Result.Value, length(aValue));
for i := 0 to High(aValue) do
Result.Value[i] := aValue[i] * 2;
end;
var
ml1, ml2: TmList;
begin
ml1 := Create([3, 4, 5]);
ml2 := ml1.Bind(Increment).Bind(double);
Writeln(ml1.ToString, ' -> ', ml2.ToString);
readln;
end.</lang>
{{out}}
<pre>[ 3, 4, 5] -> [ 8, 10, 12]</pre>
=={{header|EchoLisp}}==
Our monadic lists will take the form (List a b c ...), ie raw lists prefixed by the List symbol.
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