Function help

[Inugami]

Hello i recently started to use functions but do not understand the concept. I have worked on a project out of a book that adds coins(quarters, dimes, nickels, pennies) and adds them all up using a function. This is what i have done:

Dim sngCalculate As Single
--------------------------------------------------------------------------
Private Sub btnAddCoins_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAddCoins.Click
Dim sngQuarters As Single = Val(Me.txtValue1.Text)
Dim sngDimes As Single = Val(Me.txtValue2.Text)
Dim sngNickels As Single = Val(Me.txtValue3.Text)
Dim sngPennies As Single = Val(Me.txtValue4.Text)

sngQuarters = sngQuarters * 25
sngDimes = sngDimes * 5
sngNickels = sngNickels * 10
sngPennies = sngPennies * 1

Me.lblAnswer.Text = Calculate(sngCalculate)
End Sub
--------------------------------------------------------------------------
Function Calculate(ByVal sngQuarters As Single, ByVal sngDimes _
As Single, ByVal sngNickels As Single, ByVal sngPennies As Single) As Single

sngCalculate = sngQuarters * sngDimes * sngNickels * sngPennies
Return sngCalculate
End Function

End Class

This does not work and i am uncertain of if i am doing the function correctly. Any help would be greatly appreciated. So far it adds everything to 0.

[kleinma]

functions return a value. That means using that global variable sngCalculate is not needed at all.

The other thing is, before you are calling this function, you are already calculating the money value of the change that was entered, so multiplying them in your calculate function will produce wrong results. You would want to add them there right? Add up all the value of the dimes, quarters, etc. together and return the value.

I would think your calculate function would look something like this.

Also in your code, you are only trying to pass 1 value to the routine, where in reality, you need to pass the quarters, dimes, nickels and pennies to it.

Function Calculate(ByVal sngQuarters As Single, ByVal sngDimes _
                     As Single, ByVal sngNickels As Single, ByVal sngPennies As Single) As Single
        Return sngQuarters + sngDimes + sngNickels + sngPennies
    End Function

another suggestion is to move your money multiplying from the button click sub routine into your calculate routine, as that is a better place for it.

[Inugami]

oh wow, why did i multiply? I'm so stupid xD

thanks for the help.

[kleinma]

no problem..

And welcome to the forums

[Inugami]

Thanks but i have another problem that i dont understand
Me.lblAnswer.Text = Calculate(sngCalculate)

Its underlined and says


whats the problem ><?

[kleinma]

the problem is your calculate function is expecting you to pass your quarters, dimes, nickels, and pennies variables (in that order) to it. Not just one sngCalculate variable (which as I said is not needed at all.. you should just delete it from your code)

Me.lblAnswer.Text = Calculate(sngQuarters, sngDimes, sngNickles, sngPennies).ToString

[Inugami]

Ah yes thank you, i did the exact same thing but without the .ToString

What is the need or purpose of adding .ToString at the end?

[kleinma]

.ToString converts a numeric data type (single) into a string, because the labels text property is a string.

Because the number value 123 and the string "123" are not the same thing, but either could be converted to the other form using the various conversion functions found right in the framework.

Like

Dim MyString as String = (123).ToString
'or
Dim MySingle as Single = convert.tosingle("123")

You probably don't HAVE to do this in your code because you are likely coding with Option Strict Off.

If you code with Option Strict On, then the IDE would complain about your code and tell you it can't just convert the number value to a string value, which is why you call .ToString.

I always recommend people code with option strict on, but for whatever reason, MS has it off by default in VB.NET, likely do appease VB6 programmers moving to .NET, where things like option strict did not exist.

However someone new to programming would likely never know about this feature unless someone told them, or they stumbled across it.

Here is the documentation for Option Strict.
http://msdn.microsoft.com/library/de...tionstrict.asp

I suggest turning it on, because it will lead to better code writing, and less weird errors later...