Dynamic substitution of Variables in expressions

arun_mibuso

Hi All,

Does anybody know how to do substitution of variables in string expressions.

E.g.

TXT = 'a*b + c*2'; // TXT is a string

a := 10;
b := 5;
c := 7;

d:= FUNCTION(TXT);

// is there any function which will substitute a, b & c of the string with the corresponding variables and evaluate the expression and set value of d to 64 [10*5 + 7*2]

Please help. Thanx in advance

ARUN

kriki

You might use STRSUBSTNO but not with a,b,c but with %1,%2,%3.

And then use the DLL of MS Excel to calculate the result in Excel and get it back to Navision.

Luc_VanDyck

You could have a look at codeunit 8 AccSchedManagement, function EvaluateExpression. I remember I used this Acc. Schedule functionality where you can define your Column Layouts with formula's, for a project where they needed some form of calculation.

Using kriki's suggestion would be much easier (using Excel in the background to do the calculation).

arun_mibuso

Hi Luk & Kriki,

Thank you very much for your answers.
I was actually looking for something within navision.

Thanx again.
ARUN

Albertvh

Hi Arun

I used Luc's idea and created a codeunit that looks like this

Documentation()

OnRun()
a := 10;
b := 5;
c := 7;
Text := STRSUBSTNO('%1 * %2 + %3 * 2',a,b,c);
d := PassText(Text);
MESSAGE('Text   = %2\Result = %1',FORMAT(d),Text);

PassText(PassedText : Text[250]) : Decimal
Formula := PassedText;
Exp := FALSE;
IF (STRPOS(Formula,'+') > 0) OR
   (STRPOS(Formula,'-') > 0) OR
   (STRPOS(Formula,'*') > 0) OR
   (STRPOS(Formula,'^') > 0) OR
   (STRPOS(Formula,'/') > 0) THEN
  Exp := TRUE;
EXIT(Calculate(Formula,Exp));

Calculate(Expression : Text[250];PassIsExpression : Boolean) : Decimal
Result := 0;
Expression := DELCHR(Expression,'=',' ');
IF STRLEN(Expression) > 0 THEN BEGIN
  Parantheses := 0;
  IsExpression := FALSE;
  Operators := '+-*/^';
  OperatorNo := 1;
  REPEAT
    i := STRLEN(Expression);
    REPEAT
      IF Expression[i] = '(' THEN
        Parantheses := Parantheses + 1
      ELSE
        IF Expression[i] = ')' THEN
          Parantheses := Parantheses - 1;
      IF (Parantheses = 0) AND (Expression[i] = Operators[OperatorNo]) THEN
        IsExpression := TRUE
      ELSE
        i := i - 1;
    UNTIL IsExpression OR (i <= 0);
    IF NOT IsExpression THEN
      OperatorNo := OperatorNo + 1;
  UNTIL (OperatorNo > STRLEN(Operators)) OR IsExpression;
  IF IsExpression THEN BEGIN
    IF i > 1 THEN
      LeftOperand := COPYSTR(Expression,1,i - 1)
    ELSE
      LeftOperand := '';
    IF i < STRLEN(Expression) THEN
      RightOperand := COPYSTR(Expression,i + 1)
    ELSE
      RightOperand := '';
    Operator := Expression[i];
    LeftResult :=
      Calculate(
        LeftOperand,FALSE);
    RightResult :=
      Calculate(
        RightOperand,FALSE);
    CASE Operator OF
      '^':
        Result := POWER(LeftResult,RightResult);
      '*':
        Result := LeftResult * RightResult;
      '/':
        IF RightResult = 0 THEN
          Result := 0
        ELSE
          Result := LeftResult / RightResult;
      '+':
        Result := LeftResult + RightResult;
      '-':
        Result := LeftResult - RightResult;
    END;
  END ELSE
    IF (Expression[1] = '(') AND (Expression[STRLEN(Expression)] = ')') THEN
      Result :=
        Calculate(COPYSTR(Expression,2,STRLEN(Expression) - 2),FALSE)
    ELSE
      EVALUATE(Result,Expression);
END;
EXIT(Result);

You would of course delete the OnRun function and only run the codeunit as follows

Text := STRSUBSTNO('%1 * %2 + %3 * 2',a,b,c);
d := c.passtext(text);

Maybe you could use this or if need be I can mail you the fob file.

Albert

Soumyadip

Can you send it to me plz...

my mail id is: soumyadip AT rediffmail DOT com

Thank you