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by dahfizz 1544 days ago
You're definitely stretching here. I could just as easily argue that "all of main memory" is the output of any function. Therefore every function is a pure function, and C is a function language. Using your definition, the concept of functional programming is meaningless.

Main memory is state. Registers and cache are state. The entire purpose of the CPU is to mutate state.
1 comments
nightski 1544 days ago
No, I don't believe you could argue C is purely functional by framing memory as the output of the function because C doesn't treat it as such. Memory in C can be changed even if it is not listed in the inputs or outputs of the function.

He's not really stretching the definition, that's just the lens through which FP looks at the world.

Of course there is state. FP doesn't prohibit state, it just makes it explicit and referentially transparent. But this is in the semantics, not the execution model of the program.

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dahfizz 1543 days ago
> Memory in C can be changed even if it is not listed in the inputs or outputs of the function.

If we are going to nitpick syntax, nothing about `mov eax ebx` lists main memory as output. In fact, mov doesn't even have an 'output'.

If you want to model mov as a function with the implicit output of "all of main memory", then you can do the same with any arbitrary C function. If you can't make that leap for C, then you can't make that leap for assembly.

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nightski 1543 days ago
It's not syntax, it is semantics. There is a lot to programming language theory/design and this is all formalized. C does not have the semantics you are describing in the formal specifications (C99, etc..). Could they have developed a version of C with these semantics? Possibly. Rust was a step in that direction with it's borrow checker.
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dahfizz 1543 days ago
Yes, and my whole point is that assembly does not have those semantics either. The computer is an imperative machine.
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TuringTest 1543 days ago
The computer is not an imperative machine. It's a physical machine that you describe with an imperative representation in your mind. Can you tell the difference, or are you unaware of the map-territory distinction going on?

Functional programmers are simply choosing to use a different style of map, but we both represent the same reality.

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dehrmann 1543 days ago
According to Wikipedia, "the hardware implementation of almost all computers is imperative."

https://en.wikipedia.org/wiki/Imperative_programming

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