>Yes. And just like in real life if you want to do business - you have to accept some degree of debt to get anywhere. Trying to predict the future and make the perfect design upfront is almost always a mistake.

And I'm saying FP offers a way to avoid this type of debt all together. You can accept it if you want. I'm just telling you of a methodology that avoids debt: A perfect initial design that doesn't need refactoring.

>We can't communicate without establishing some objective measures. Otherways we'll just spew contradictory statements at each other. These toy examples are bad, obviously, but the fact that there's basically no big functional programs speaks for itself.

Sure then I'm saying lines of code is not an objective measure. Let's establish another objective measure that's more "good": The amount of lines of structural changes made to the original design. It's universally accepted that lines of code aren't really a good measure but it's one of the few quantitative numbers. So I offer a new metric. How many lines of the original design did you change? In mine: 0.

I don't want to write the psuedocode for it, but let's say doABCD() is called in 1000 different places as well. Then in the imperative code you have 1000 lines of changes thanks to a structural change. Structural design changes leads to exponential changes in the rest of the code hence this is a better metric.

That's an objective measure showing how FP is better. I didn't take any jumps into intuition here and I am sticking with your definition of an "objective measure"

>And that's perfectly fine.

That's just opinion. Surely you see the benefit of a perfect initial design such that code never needs refactoring. It happens so often in business that it's normal to refactor code. But I'm saying here's a way where you perfect your design in the beginning. That's the whole point of modularity right? It's an attempt to anticipate future changes and minimize refactoring and FP offers this in a way Objectively better than imperative. If your always changing the design when a new feature was added what's the point of writing modular and well designed code? Just make it work and forget about everything else because it's "okay" to redesign it.

>According to your definition of "code changed" if I duplicate everything and leave the old lines there - no code was changed which means the design was perfect :)

But then you introduced more technical debt. You duplicated logic. What if I want to change the "a" operation. Now I have to change it for both doABCD and doABCD2. Let's assume I have doABCD3 and 4 and 5 and 6 all the way to 20 who all use operation "a" and now they all have to be changed because they all used duplicate code.

Let's not be pedantic. Refactoring code is a sign of technical debt from the past. But also obviously duplicating code is also known to be technical debt.

>I don't think we'll get to a point where we agree about this.

Sure but under objective measures FP has better metrics. Opinion wise we may never agree, but objectively if we use more detailed and comprehensive rules for the metric, FP is better.

>One last thing I'd like to know is why do you think nobody writes big projects in functional languages?

Part of the reason is because of people with your mentality who don't understand. It's the same reason why the US doesn't use metric. Old cultural habits on top of lack of understanding.