Delphi Basics : CompareValue command

DelphiBasics

CompareValue
Function

Compare numeric values with a tolerance

Math unit

1	function CompareValue(const A, B Integer\|Int64):TValueRelationship;
2	function CompareValue (const A, B Single\|Double\|Extended; delta Single\|Double\|Extended:TValueRelationship;

Description

CompareValue allows floating point numbers to be compared in a tolerant way. If the two numbers are close enough together, they are deemed to be equal. The delta value is the permitted tolerance.

There seems no point to the author in providing the Integer version of this function with no delta.

TValueRelationship supports the following values :

LessThanValue	-1
EqualsValue	0
GreaterThanValue	1

Related commands

Max		Gives the maximum of two integer values
Min		Gives the minimum of two integer values
Mean		Gives the average for a set of numbers

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Example code : Comparing floating point numbers

var
  A : Single;
  B : Single;
  C : Single;

begin
  A := 23.0;
  B := 23.0;
  C := 23.1;

  // Compare 2 equal floats
  case CompareValue(A, B) of
    LessThanValue    : ShowMessage('A < B');
    EqualsValue      : ShowMessage('A = B');
    GreaterThanValue : ShowMessage('A > B');
  end;

  // Compare 2 unequal floats
  case CompareValue(A, C) of
    LessThanValue    : ShowMessage('A < C');
    EqualsValue      : ShowMessage('A = C');
    GreaterThanValue : ShowMessage('A > C');
  end;

  // Compare 2 unequal floats - but allow for a difference of up to +/- 0.2
  case CompareValue(A, C, 0.2) of
    LessThanValue    : ShowMessage('A < C');
    EqualsValue      : ShowMessage('A = C');
    GreaterThanValue : ShowMessage('A > C');
  end;
end;

Show full unit code

  A = B
  A < C
  A = C