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Comment by akkartik | Hacker News Reader

"The omission of variable declarations has nothing to do with dynamic typing."

I was inclined to say this as well when I was critiquing the first point (http://news.ycombinator.com/item?id=3633351). But on further thought, just about the only dynamic language that flags assignment to a typo'd variable name is scheme[1]. So it seems like a significant correlation.

[1] Not common lisp. Does clojure?

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JavaScript with "use strict"--which is basically the modern version of JavaScript, but has to be enabled explicitly because of backwards compatibility--also warns you about assigning a variable that hasn't been declared. Just shows that JavaScript really was influenced by Scheme :).

Ditto for Perl. And with modern Perl(s) this can be switched on with new language features using...

  use 5.010;  # or 5.012 or 5.014 and soon 5.016

Ah, thanks both.

In both languages, the use of a variable is almost always preceded by a binding of that variable to a symbol or var using the "let" form. This accounts for most uses of variables, and attempting to access a misspelled variable will flag an error at compile-time.

With regard to destructive assignment, most Common Lisp compilers warn on setf calls when executed against unbound symbols. Clojure doesn't have even have assignment in the sense discussed here (refs are bound before use, and the compiler enforces this).

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