posted 07-06-2000 02:14 PM         

An inefficient way to do it would be to declare a variable for each cell, and parsing/evaluating cells and dependant cells each time. Some have discovered that there’s a significant speed penalty when you define large numbers of variables (this affects the speed of ucParse, and other functions that depend on ucParse, such as ucEval. But the speed of ucEvaluate is not affected).

Anyway, building on last month’s concept of UCalc “arrays”, spreadsheet cells can be mapped out onto an array. Also, instead of repeatedly parsing/evaluating cells with ucEval, cells need not be parsed more than once when they are changed. A cell is parsed with ucParse, and then that cell, along with all dependent cells are quickly updated with ucEvaluate, which is significantly faster.

The README.TXT file that comes with the sample spreadsheet program contains more explanations. The zip file includes a simple ready-to-run spreadsheet program in Visual Basic, C++ Builder, and Delphi. The code is just a quick primer. A number of additional things can be done to make the spreadsheet more sophisticated.

posted 07-31-2000 03:31 PM         

consider the scenario:
In the spreadsheet, if you have a var 'x' in cell 1 which has a dependant var 'y' in cell 2, but, var y has a math expression as it's val, but, the math expr uses var 'x' from cell 1. This is a direct 1->1 dependancy, updating the value of 'x' will update 'y' which in-turn will update the value of 'x'.
To complicate things, how about if there is a third variable 'z' whcih will create a dependancy list as follows:

x->y->z->x.

Any suggestions other than checking thoroughly among the dependant variable list to avoid creating such a loop ?

I would like to hear from anyone, if they have any better solutions to the potential loop problem.

posted 08-13-2000 10:16 PM         

If you are using the VB sample, then in Module1 (ucSpread.Bas), beneath the line that says: Public CellEq$(), ... , place
this:

Public CircularCount

Now within the Sub SetCellValue routine, place this line as one of the first statements of the Sub routine:

CircularCount = 0

Now at the beginning of the UpdateDepCells routine, place the following lines of code:

code:

---

CircularCount = CircularCount + 1
If CircularCount = 100 Then Exit Sub

---