Best Practice for Calculations

Let us consider calculating profit as example

Profit := Income-Expenditure;

There is no guarantee that Income and Expenditure data will always have a numeric data type. Some users may prefer to use ‘No Income’ or ‘No Expenditure’ values

The best way to avoid problems with data quality is to follow the pattern below.

Create variables for every input parameter.
Assign input parameters to variables inside try expect block
Perform calculations
Return value

Example:

Var
vIncome: Float;
vExpenditure: Float;

begin
// Converting strings to Floats
Try
vIncome:=Income;
except
vIncome:=0;
end;

try
vExpenditure:=Expenditure;
except
vExpenditure:=0;
end;

// Calculation

Result := vIncome-vExpenditure;
end;