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0 pointscanes1234568y ago0 comments

I think I understand the point you are making but this is way more confusing for me. Partly this can be blamed on imperative lanuages and = vs ==.

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sbergot8y ago

Not that in mutable languages == can either mean storage equality or value equality. In immutable languages there is only value equality.

giesch8y ago

In a procedural language:

x == 3 means: Take the value out of the box x. Is it 3?

x = 3 means: x is a box, put 3 in it. The 3 lasts forever, or until someone changes it.

In a functional language:

x = 3 means: Take the value out of box x. Is it 3?

let x = 3 in [...] means: x is a box, put a 3 in it. The 3 lasts for only the [...], but cannot be undone.

nybble418y ago

Correction: In a functional language (specifically Haskell):

  x = 3 means: x is defined as 3.
  x == 3 means: Is x equal to 3?
  let x = 3 in [...] means: within the scope of [...], x is defined as 3.

There is no specific point where something is "put into the box" or "taken out of the box". In fact, there is no "box". The functional programming concept of "bindings" does not correspond to the imperative concept of "variables", not even the oxymoron known was "constant variables". (If you want variables in Haskell you need IORef or STRef, where the load and store operations are explicit monadic actions.)

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