Use a variable as an operator - Powershell

Question

I startet with Powershell and tried to do a simple calculator.

This is what I have:

Function ReturnRes ($x,$y,$z)
{
    $res= [float] $z [float]$y
    return $res
}

Write-Host $res
$var1 = Read-Host "Zahl1"
$var2 = Read-Host "Zahl2"
$op = Read-Host "Operator(+-*/)"

ReturnRes -x $var1 -y $var2 -z $op

But I can't use the $z variable as an operation...

Any ideas?

Answer 1

You can use Invoke-Expression:

PS C:\> $x,$y,$op = '1.23','3.21','+'
PS C:\> Invoke-Expression "$x$op$y"
4.44

Make sure you validate the input:

Function Invoke-Arithmetic 
{
    param(
        [float]$x,
        [float]$y,
        [ValidateSet('+','-','*','/')]
        [string]$op
    )

    return Invoke-Expression "$x $op $y"
}

Answer 2

Here's another solution, add a default case to the switch to handle non-valid operators:

Function ReturnRes($x,$y,$z){
    switch($z){
        "+" {[float]$x + [float]$y}
        "-" {[float]$x - [float]$y}
        "*" {[float]$x * [float]$y}
        "/" {[float]$x / [float]$y}
    }
}

Write-Host $res
$var1 = Read-Host "Zahl1"
$var2 = Read-Host "Zahl2"
$op = Read-Host "Operator(+-*/)"

ReturnRes -x $var1 -y $var2 -z $op