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fpvectorial: Implements support for infix to RPN formula conversion for left-associative operators

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git-svn-id: trunk@44394 -
This commit is contained in:
sekelsenmat 2014-03-10 09:12:37 +00:00
parent 796e552c53
commit 5d6b6286f1
1 changed files with 45 additions and 2 deletions
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47
components/fpvectorial/fpvectorial.pas
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@ -789,6 +789,8 @@ type
procedure Render(ADest: TFPCustomCanvas; ARenderInfo: TvRenderInfo; ADestX: Integer = 0;
ADestY: Integer = 0; AMulX: Double = 1.0; AMulY: Double = 1.0); virtual;
procedure GenerateDebugTree(ADestRoutine: TvDebugAddItemProc; APageItem: Pointer); virtual;
class function GetPrecedenceFromKind(AKind: TvFormulaElementKind): Byte; // 0 is the smallest precedence
class function IsLeftAssociativeFromKind(AKind: TvFormulaElementKind): Boolean;
end;
{ TvFormula }
@ -1398,7 +1400,7 @@ var
GvVectorialFormats: array of TvVectorialFormatData;
const
FormulaOperators = [fekSubtraction, fekMultiplication, fekSum, fekFraction];
FormulaOperators = [fekSubtraction, fekMultiplication, fekSum, fekFraction, fekRoot, fekPower];
procedure RegisterVectorialReader(
AReaderClass: TvVectorialReaderClass;
@ -4485,6 +4487,29 @@ begin
end;
end;
// http://en.wikipedia.org/wiki/Shunting-yard_algorithm
class function TvFormulaElement.GetPrecedenceFromKind(
AKind: TvFormulaElementKind): Byte;
begin
Result := 0;
case AKind of
fekSubtraction, fekSum: Result := 2;
fekMultiplication, fekFraction: Result := 3;
//fekRoot, // A root. For example sqrt(something). Number gives the root, usually 2, and inside it goes a Formula
fekPower: Result := 4;
end;
end;
// See http://en.wikipedia.org/wiki/Shunting-yard_algorithm
class function TvFormulaElement.IsLeftAssociativeFromKind(
AKind: TvFormulaElementKind): Boolean;
begin
Result := True;
case AKind of
fekPower: Result := False;
end;
end;
{ TvFormula }
procedure TvFormula.CallbackDeleteElement(data, arg: pointer);
@ -4562,12 +4587,30 @@ var
procedure PopFromStackIntoList(APopTopOperators: Boolean; APopUntilParenteses: Boolean);
var
lElement: TvFormulaElement;
lAllowContinue: Boolean;
begin
while OperatorStack.Count > 0 do
begin
lElement := OperatorStack.Pop() as TvFormulaElement;
if APopTopOperators and (not (lElement.Kind in FormulaOperators)) then Exit;
// while there is an operator token, o2, at the top of the stack, and
// either o1 is left-associative and its precedence is equal to that of o2,
// or o1 has precedence less than that of o2,
if APopTopOperators then
begin
if not (lElement.Kind in FormulaOperators) then Exit;
lAllowContinue := TvFormulaElement.IsLeftAssociativeFromKind(lElement.Kind)
and (TvFormulaElement.GetPrecedenceFromKind(lElement.Kind) =
TvFormulaElement.GetPrecedenceFromKind(CurItem.Kind));
lAllowContinue := lAllowContinue or
(TvFormulaElement.GetPrecedenceFromKind(lElement.Kind) >
TvFormulaElement.GetPrecedenceFromKind(CurItem.Kind));
if not lAllowContinue then Exit;
end;
if APopUntilParenteses and (lElement.Kind = fekParentesesOpen) then Exit;
FElements.Add(lElement);
end;
end;