[mrw]

This article made me realise that I don't know how to perform step-through debugging on chained of operations on Streams in Java, so I looked it up. I found out that there's Stream Trace Dialog in IntelliJ IDEA [0]. I guess it proves your point that working with Stream API requires additional tooling in cases when the code doesn't 'just work'.

[0]: https://www.jetbrains.com/help/idea/analyze-java-stream-oper...

[chii]

the ideal scenario with functional programming like this is to reason about the code, and may be algebraically model it mentally so that you "know" it works.

But i find a lot of programmers don't do that - but instead write a first version which they don't truly understand (or understand completely), and then use stepped debugging to tweak the program until they get to a verison that works to their desired outcome.

[BiteCode_dev]

Ideal scenarios rarely exist IRL. You may be in a rush. Inexperienced. Tired. On a problem you don't completely understand yet. With incomplete information. Exploring data or the problem space. Experimenting with an API. Trying to debug the code your colleague wrote, or a bug in the underlying lib.

That's why practicality beats purity in the vast majority of situations.

There is a place for purity, but you need a hell of a setup.