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IMHO in a declarative language your example should be an error. You defined x twice. Intentionally or not, this is confusing, for others and for you in a week w

IMHO in a declarative language your example should be an error. You defined x twice. Intentionally or not, this is confusing, for others and for you in a week when you have to look at the code again. Also, why should the second binding override the first? You introduced a temporal dimension where later lines of code somehow override earlier lines of code. That is not a necessity in a declarative language. It may be how we humans read text (from top to bottom), but it does not mean the computer has to process it in the same way.

jcelerier 6y ago
> IMHO in a declarative language your example should be an error. You defined x twice. Intentionally or not, this is confusing, for others and for you in a week when you have to look at the code again. c'mon, this is an example in a forum post ! of course it doesn't make sense in real life. real life is distance := computeDistanceToCenterOfScreen(cursorPosition) text := "the current distance is: " + distance but that just muddies the waters needlessly > Also, why should the second binding override the first? You introduced a temporal dimension where later lines of code somehow override earlier lines of code. yes, some languages work like that, but it's not the point - either you assume that you can update values in your declarative bindings like that, or you have to define your binding in terms of some external behaviour that will change in magic ways, which again would not be very nice to do as a simple forum post example
YeGoblynQueenne 6y ago
>> IMHO in a declarative language your example should be an error. You defined x twice. This would be an error in a language with immutable data structures. Declarative and immutable are not the same thing and there is nothing that says a declarative language must have immutable data structures.
- sp332 6y ago
  I think the idea is that declarative statements use "equals" like math uses equals, not as assignment. If you say x = 1 and then later say x = 2, that is a contradiction. Usually if you evaluate each statement in order from top to bottom, that is procedural programming. And if you don't do that, it's hard to assign multiple values to one variable because you need a way for the compiler to know when the variable has each value.
- the_af 6y ago
  > This would be an error in a language with immutable data structures It's an error from the point of view of equational thinking; (im)mutabilty is not involved. The name `x` cannot be 1 and 3 simultaneously. It's either 1 or 3. So in the allegedly declarative program, the programmer first claimed name `x` is bound to the value 1, but later claimed it's 3. That's the error. This has nothing to do with mutating data structures. Like the sibling comment notes, there is not "first-this-then-that" order of evaluation, so you cannot read this as "first `x` means 1, but later it means 3", because there are no notions of "first" and "later".

jcelerier 6y ago

> IMHO in a declarative language your example should be an error. You defined x twice. Intentionally or not, this is confusing, for others and for you in a week when you have to look at the code again. c'mon, this is an example in a forum post ! of course it doesn't make sense in real life. real life is distance := computeDistanceToCenterOfScreen(cursorPosition) text := "the current distance is: " + distance but that just muddies the waters needlessly > Also, why should the second binding override the first? You introduced a temporal dimension where later lines of code somehow override earlier lines of code. yes, some languages work like that, but it's not the point - either you assume that you can update values in your declarative bindings like that, or you have to define your binding in terms of some external behaviour that will change in magic ways, which again would not be very nice to do as a simple forum post example

YeGoblynQueenne 6y ago

>> IMHO in a declarative language your example should be an error. You defined x twice. This would be an error in a language with immutable data structures. Declarative and immutable are not the same thing and there is nothing that says a declarative language must have immutable data structures.

sp332 6y ago
I think the idea is that declarative statements use "equals" like math uses equals, not as assignment. If you say x = 1 and then later say x = 2, that is a contradiction. Usually if you evaluate each statement in order from top to bottom, that is procedural programming. And if you don't do that, it's hard to assign multiple values to one variable because you need a way for the compiler to know when the variable has each value.
the_af 6y ago
> This would be an error in a language with immutable data structures It's an error from the point of view of equational thinking; (im)mutabilty is not involved. The name `x` cannot be 1 and 3 simultaneously. It's either 1 or 3. So in the allegedly declarative program, the programmer first claimed name `x` is bound to the value 1, but later claimed it's 3. That's the error. This has nothing to do with mutating data structures. Like the sibling comment notes, there is not "first-this-then-that" order of evaluation, so you cannot read this as "first `x` means 1, but later it means 3", because there are no notions of "first" and "later".