First-class functions: Difference between revisions

=={{header|Delphi}}==

{{libheader| System.SysUtils}}

{{libheader| System.Math}}

{{Trans|C#}}

<lang Delphi>

program First_class_functions;

{$APPTYPE CONSOLE}

uses

System.SysUtils,

System.Math;

type

TFunctionTuple = record

forward, backward: TFunc<Double, Double>;

procedure Assign(forward, backward: TFunc<Double, Double>);

end;

TFunctionTuples = array of TFunctionTuple;

var

cube, croot, fsin, fcos, faSin, faCos: TFunc<Double, Double>;

FunctionTuples: TFunctionTuples;

ft: TFunctionTuple;

{ TFunctionTuple }

procedure TFunctionTuple.Assign(forward, backward: TFunc<Double, Double>);

begin

self.forward := forward;

self.backward := backward;

end;

begin

cube :=

function(x: Double): Double

begin

result := x * x * x;

end;

croot :=

function(x: Double): Double

begin

result := Power(x, 1 / 3.0);

end;

fsin :=

function(x: Double): Double

begin

result := Sin(x);

end;

fcos :=

function(x: Double): Double

begin

result := Cos(x);

end;

faSin :=

function(x: Double): Double

begin

result := ArcSin(x);

end;

faCos :=

function(x: Double): Double

begin

result := ArcCos(x);

end;

SetLength(FunctionTuples, 3);

FunctionTuples[0].Assign(fsin, faSin);

FunctionTuples[1].Assign(fcos, faCos);

FunctionTuples[2].Assign(cube, croot);

for ft in FunctionTuples do

Writeln(ft.backward(ft.forward(0.5)):2:2);

readln;

end.</lang>

{{out}}

<pre>0.50

0.50

0.50</pre>