# Non-declared variables **URL:** \ **Category:** Ruby\ **Created:** [October 16, 2006, 1:42pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323 "2006-10-16T13:42:24Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Avatar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@Avatar](https://www.ruby-forum.com/u/Avatar)\ **Post date:** [October 16, 2006, 1:42pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323/1 "2006-10-16T13:42:24Z")
I would like to hear people’s opinions on the ability to use variables without declaring them in dynamic languages like Ruby. It would seem to me that an argument for non-declared local variables that typically occupy a small scope could be made. But, class variables? What is the benefit in allowing for runtime definition of class variables? Are there real tangible benefits that non-declared, dynamically typed (at binding time) variables provide? Or do dynamic variables simply create less compile time errors and more (harder to catch) runtime errors? Thoughts? ---
**Author:** ![Avatar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@Avatar](https://www.ruby-forum.com/u/Avatar)\ **Post date:** [October 16, 2006, 3:32pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323/2 "2006-10-16T15:32:49Z")
On Mon, 16 Oct 2006 04:38:09 -0700, Avatar wrote: > create less compile time errors and more (harder to catch) runtime > errors? > > Thoughts? I was programming in Java last week, and writing typed code. I found that after about an hour of coding, my code would have worked correctly (it would have been less time if Java supported operator overloading the way ruby does), but I still had to spend another hour getting the types appropriately declared, and typecasting things correctly as I pulled objects out of their various collections. C++ can be worse. I wanted to use the Boost Spirit library for CFG parsing, and found that I couldn’t read the compile errors I was getting because 90% of the text was multiply nested template types. The C++ Standard Template Library uses templates so much to get close to Ruby’s flexibility, but the result is still more complicated than Ruby, impossible to debug, and less flexible. At that point, why not go all the way to a dynamically typed language? –Ken B. ---
**Author:** ![Avatar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@Avatar](https://www.ruby-forum.com/u/Avatar)\ **Post date:** [October 16, 2006, 3:43pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323/3 "2006-10-16T15:43:20Z")
> C++ can be worse. I wanted to use the Boost Spirit library for CFG > parsing, and found that I couldn’t read the compile errors I was > getting because 90% of the text was multiply nested template types. The C++ > Standard Template Library uses templates so much to get close to Ruby’s > flexibility, but the result is still more complicated than Ruby, > impossible to debug, and less flexible. At that point, why not go all the > way to a dynamically typed language? Because then you’re a different language with different use cases with different benefits and drawbacks. Boost is an incredibly good set of libraries, with an extremely high level of QA. The great tragedy is that facilities like this were not part of a C++ standard library a decade ago. Still, the C++ Standards Committee are well aware of the problems that templates cause with respect to indecipherable error messages, which is why the new system of concepts has been proposed for C++0x, so the compiler can flag straight away when you’ve tried to instantiate a template parameter that won’t work. Also, if you’re a genius, you can use template metaprogramming to do some really spanky compile-time shenanigans. Martin ---
**Author:** ![Avatar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@Avatar](https://www.ruby-forum.com/u/Avatar)\ **Post date:** [October 16, 2006, 4:13pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323/4 "2006-10-16T16:13:43Z")
On 10/16/06, Avatar [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I would like to hear people’s opinions on the ability to use variables > without declaring them in dynamic languages like Ruby. You mean without declaring their _type_, right? It’s more accurate to say simply that variables have no type in Ruby; Rather the variable’s contents have a type. In any case, Ruby requires that variables be declared before use just as any decent language worth the name does. Martin ---
**Author:** ![Avatar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@Avatar](https://www.ruby-forum.com/u/Avatar)\ **Post date:** [October 16, 2006, 4:05pm UTC](https://www.ruby-forum.com/t/non-declared-variables/72323/5 "2006-10-16T16:05:41Z")
Avatar wrote: > I would like to hear people’s opinions on the ability to use variables > without declaring them in dynamic languages like Ruby. Could you clarify what you mean by that? Are you concerned about methods like #instance\_variable\_set and #class\_variable\_set? Or more generally about the fact that code like: class Foo @bar = 12 end creates an instance variable on the fly at runtime, without requiring some sort of instance @bar line that ‘declares’ it before use?