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API function CalcExpression(Value: String; var Res: String): Word; Evaluates Value, result is stored in Res (use StrToFloat function from SysUtils unit to convert string value into it's float representation). Returns C_NOERROR if there is no error, otherwise it will return one of error codes. Example:
procedure TForm1.EvaluateClick(Sender: TObject);
var
ErrorCode: Word;
Res: String;
begin
Memo1.Lines.Clear;
ErrorCode := CalcExpression('1+2', Res);
if ErrorCode <> C_NOERROR then
begin
Memo1.Lines.Add('Cannot evaluate expression: ' + CalcErrorToStr(ErrorCode));
Exit;
end else
Memo1.Lines.Add('Result: ' + Res)
end;
Memo1 should contain 'Result: 3'
function CalcGraphExpression(Value: String; X: Extended; var Res: String): Word;Works as CalcExpression but replaces x in Value with extended variable X. Example:
procedure TForm1.EvaluateClick(Sender: TObject);
var
ErrorCode: Word;
Res: String;
begin
Memo1.Lines.Clear;
ErrorCode := CalcExpression('sin(pi/2)', Res);
if ErrorCode <> C_NOERROR then
begin
Memo1.Lines.Add('Cannot evaluate expression: ' + CalcErrorToStr(ErrorCode));
Exit;
end else
Memo1.Lines.Add('Result: ' + Res)
end;
Memo1 should contain 'Result: 1'
function CalcErrorToStr(Error: Word): String;Converts error code returned by CalcExpression and CalcGraphExpression to it's string representation. |
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