(0) Functional programming is expressing computation as the evaluation of functions. A language is “functional” to the extent it allows you to do functional programming.
(1) A function is a mapping from values to values. To express computation as the evaluation of functions, you need a rich universe of values: not just primitive ones like integers and object references, but also tuples, lists, trees, etc.
(2) Values are timeless entities that are distinguished from each other structurally. For example, it makes no sense to distinguish “this list [1,2,3]” from “that list [1,2,3]”, because both have the same structure - the same parts. Thus, what Python calls “tuples” and “lists” are not really tuple values and list values.
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@_9jgl
Let's see how equal they remain in a timeless fashion:
xs = [1,2,3]
ys = [1,2,3]
zs = ys
send_to_another_thread(xs,ys,zs)
print(xs == ys) # who knows
print(ys == zs) # True
print(xs is ys) # False
print(ys is zs) # True
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@lmm
> This is by no means the only way to write Python
This is not the problem. The problem is that Python doesn't have compound values. Values are a matter of semantics, and semantics is a matter of how the language is defined, not how you choose to program in it.
Would you mind expanding on this? I'm not sure I really understand what you mean – if we have two lists a = [1,2,3] and b = [1,2,3], then a == b, so I don't see how Python is distinguishing them from each other.
{ok, integer()} | {err, string()}