Question

Why vb prints out 1??? when d is a double aproximation to 1? shoudnt be 0.99999 or something similar? what if I really need the float value? and how could I print it?

Dim d As Double

For i = 1 To 10
    d = d + 0.1
Next

MsgBox(d)
Console.WriteLine(d)

thanks

Answer 1

When using MsgBox or Console.WriteLine, double.ToString() is called in order to convert the double to a string.

By default this uses the G format specifier.

The general (“G”) format specifier converts a number to the most compact of either fixed-point or scientific notation, depending on the type of the number and whether a precision specifier is present. The precision specifier defines the maximum number of significant digits that can appear in the result string. If the precision specifier is omitted or zero, the type of the number determines the default precision, as indicated in the following table.

And:

However, if the number is a Decimal and the precision specifier is omitted, fixed-point notation is always used and trailing zeros are preserved.

When converting the infinite 0.9999999.... to a string, since it goes forever, rounding occurs, this results in 1.

A simple test is to run this:

 MsgBox((0.9999999999999999999999999).ToString())