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Comment by rapala | Hacker News Reader

I would argue that the order of declarations is part of the scoping rules. In your example the variable i is not yet in scope when the assignment is done, and thus the compiler complaints. But this is of course somewhat philosophical.

My first argument was that the order of statements is part of the lexical representation of code, and thus should effect the lexical scoping.

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I'd say the order of declarations isn't part of the scoping rules. The scoping rules are used for name resolution. In my example, both i's belong to the same scope, so the name resolution says "oh, that first i is the one in this scope, not any parent scope".

In languages like C#, a separate analysis is then done to find out if the variable is definitely assigned at each reference. This can include some sophisticated reachability analysis(how sophisticated depends on the usefulness/complexity tradeoff).

I guess it's all semantics really, but I prefer to keep the scope (ha ha) of lexical scoping rules closer to name resolution than start mixing in definite assignment and reachability analysis and the things that come with that.

It makes understanding and expressing the commonalities and differences between different language's lexical scoping a lot easier. C# is lexically scoped with blocks introducing new lexical scopes. Javascript* and Python are lexically scoped with functions introducing new lexical scopes. As an orthogonal concept, C# and Python disallow references before definite assignment, while Javascript allows it.

(*) With the dynamic 'this' caveat.

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