'This is a comment, you make one by using single quote [']  

​

'The file is an excercise to get you used to functions and parameters

'Please complete the little calculator

​

'These lines import external libraries - lots of useful code

Imports System 'import for Console

Imports Microsoft.VisualBasic 'import for vbCrLf

​

​

'The module is your program container, a standalone entity

Public Module Calculator

    'this is an example of a function, they return values

    Public Function add(v as Single, x as single)

        return x+v

    End Function

    Public Function subt(v as Single, x as single)

        return v-x

    End Function

    Public Function mul(v as Single, x as single)

        return x*v

    End Function

    Public Function div(v as Single, x as single)

        return v/x

    End Function

    Public Function fac(v as integer) as single

        dim a as single

        'If v<>0 then

        a=1

        for i=1 to v

            a=a*i

        next

        If v<0 then

            a=double.NaN

        end if

        return a

    End Function

    Public Function plus_svtz(v as Single, x as single)

        dim a as single 'a is a accumulated value

        If x<0 then 

            For i=1 to -x

                a=a-v

            Next

        Else

            For i=1 to x

                a=a+v

            Next

        End if

        'i=v

        return a

    End Function

    'this is a function that processes commands and executes other functions

    'it returns the final value

    Public Function command(v as single, c as String)

        Select Case c

        case "+"

            Console.Write(String.Format("enter value "& v &"+"))

            return add(v,Console.ReadLine())

        case "-"

            Console.Write(String.Format("enter value "& v &"-"))

            return subt(v,Console.ReadLine())

        case "*"

            Console.Write(String.Format("enter value "& v &"*"))

            return plus_svtz(v,Console.ReadLine())

        case "/"

            Console.Write(String.Format("enter value "& v &"/"))

            return div(v,Console.ReadLine())

        case "!"

            'Console.Write(String.Format("enter value "& v &"/"))

            'return fac(v,Console.ReadLine())

            return fac(v)

        case else

            Console.WriteLine("Please implement option [ " & c & " ]")

            return v

        End Select

    End Function

    'this is a Sub (Subroutine) the Sub executes the lines contatined within it, but does not return

    'this sub is special, Main() is called whenever a Module is executed,

    'if a module does not have a Main() sub, we call it a library, it cannot be executed

    Public Sub Main()

    Dim value as single

        Console.WriteLine("This is a calculator app ^_^")

        While True

            Console.WriteLine("current value ["& String.Format(value,"n")&"]"& vbCrLf &"your command[ + - * / ! ]")

            value = command(value, Console.ReadLine())

        End While

    End Sub

End Module