Approximate equality: Difference between revisions

=={{header|Delphi}}==

{{libheader| System.SysUtils}}

{{libheader| System.Math}}

The Delphi has a Math.SameValue function for compare, but all float operations use by default Extended (High precision), we need use double cast for every operation, like division, multiply and square tree.

<lang Delphi>

program Approximate_Equality;

{$APPTYPE CONSOLE}

uses

System.SysUtils,

System.Math;

const

EPSILON: Double = 1E-18;

procedure Test(a, b: Double; Expected: Boolean);

var

result: Boolean;

const

STATUS: array[Boolean] of string = ('FAIL', 'OK');

begin

result := SameValue(a, b, EPSILON);

Write(a, ' ', b, ' => ', result, ' '^I);

writeln(Expected, ^I, STATUS[Expected = result]);

end;

begin

Test(100000000000000.01, 100000000000000.011, True);

Test(100.01, 100.011, False);

Test(double(10000000000000.001) / double(10000.0), double(1000000000.0000001000),

False);

Test(0.001, 0.0010000001, False);

Test(0.000000000000000000000101, 0.0, True);

Test(double(Sqrt(2)) * double(Sqrt(2)), 2.0, False);

Test(-double(Sqrt(2)) * double(Sqrt(2)), -2.0, false);

Test(3.14159265358979323846, 3.14159265358979324, True);

Readln;

end.

</lang>

{{out}}

<pre>

1.00000000000000E+0014 1.00000000000000E+0014 => TRUE TRUE OK

1.00010000000000E+0002 1.00011000000000E+0002 => FALSE FALSE OK

1.00000000000000E+0009 1.00000000000000E+0009 => FALSE FALSE OK

1.00000000000000E-0003 1.00000010000000E-0003 => FALSE FALSE OK

1.01000000000000E-0022 0.00000000000000E+0000 => TRUE TRUE OK

2.00000000000000E+0000 2.00000000000000E+0000 => FALSE FALSE OK

-2.00000000000000E+0000 -2.00000000000000E+0000 => FALSE FALSE OK

3.14159265358979E+0000 3.14159265358979E+0000 => TRUE TRUE OK

</pre>