Using value from column to affect calculation in Power Query

[ryan_b_123]

Col 1	Col 2	Col 3	Desired Result
4	+	5	9
3	-	2	1

Let's say I have above dataset:

To do above, I could write a formula in Power QUery something like "if [col 2] = "+" then [Col 1] + [Col 3] else [Col 1] - [Col 3].  I DO NOT want this sort of solution.

Instead, I would like the value of [Col 2] to be inherent within the formula.  Perhaps with some 'mythical' formula like below:

[Col 1]    MadeUpFunction[Col 2]    [Col 3]

Is there any sort of way to affect the Power Query code using a field in your dataset?

[ryan_b_123]

Thank you, so much.  This is exactly what I am looking for.  I am curious about one thing though.

Expression.Evaluate(Text.Combine({"5","=","5"}, " "))   will return true.  Which is good.

Expression.Evaluate(Text.Combine({"hello","=","hello"}, " "))   will return an error.  "The name 'hello' doesn't exist in the current context."

Do you know why we cannot use "=" operator for alphabetical comparisons? 

[HotChilli]

There's nothing wrong with the "="
See the 3rd example
https://learn.microsoft.com/en-us/powerquery-m/expression-constant#example-3 

You need Expression.Constant

[ryan_b_123]

Thanks for the reply, but could you be a bit more specific how Expression.Constant is used?  Is this wrapped inside of the Expression.Evaluate?

The documenation is extremely short on this function and I do not know what it does exactly.

[HotChilli · Accepted solution]

Yes, there is a way.

Use Expression.Evaluate

You can build a string from the first 3 columns ( either by appending with & or use Text.Combine and then just pass that to Expression.Evaluate()