[c-cube]

The option type also prevents you from accessing the value if it's absent. Something a C union cannot do. Is there any example of options in an imperative language that would predate ML (which AFAIK introduced Some/None as the variants of option)?

[UncleMeat]

C can’t do that. But imperative programming can. Nothing about type based pattern matching is constrained to FP.

[phizy]

Not that I'm disagreeing with you in any way, but it's worth recognizing that imperative languages typically do pattern matching and type constraining in a declarative manner. So one could make an argument that what you're saying is only true because imperative languages are not forbidden from employing FP. If a language uses declarative constructs, then it's not a wholly imperative language.

[UncleMeat]

I really don't think that FP should be able to take claim for this. Or, at the very least, I don't think the sort of evangelical FP should. Type pattern matching isn't all that different from virtual dispatch if you squint.

If the FP community wants to say that impure languages have been "doing FP" for decades then great! The religious war is over! We can happily have mixed paradigm languages and move on. But that's not what I'm seeing.