# Symbols and Strings **URL:** \ **Category:** ruby-talk\ **Created:** [18 June 2012 22:09 UTC](https://rubytalk.org/t/symbols-and-strings/65710 "2012-06-18T22:09:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [18 June 2012 22:09 UTC](https://rubytalk.org/t/symbols-and-strings/65710/1 "2012-06-18T22:09:44Z")
Hello, all... A modest proposal here... I think (tentatively) that Symbol should inherit from String, and a symbol should basically be an immutable string. Reply here and/or on my blog as you see fit: [http://rubyhacker.wordpress.com](http://rubyhacker.wordpress.com) Cheers, Hal Fulton ---
**Author:** ![Eric\_Hodel1](https://avatars.discourse-cdn.com/v4/letter/e/a9adbd/32.png) [@Eric\_Hodel1](https://rubytalk.org/u/Eric_Hodel1)\ **Post date:** [18 June 2012 22:31 UTC](https://rubytalk.org/t/symbols-and-strings/65710/2 "2012-06-18T22:31:26Z")
This happened (see thread at [ruby-core:9188]) but was reverted. I can't think of the proper keywords to find the reason for the reversion. > **···** > > On Jun 18, 2012, at 15:09, Hal Fulton wrote: > > > Hello, all... > > > > A modest proposal here... I think (tentatively) that Symbol should inherit > > from String, and a symbol should basically be an immutable string. > > > > Reply here and/or on my blog as you see fit: [http://rubyhacker.wordpress.com](http://rubyhacker.wordpress.com) ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [19 June 2012 16:58 UTC](https://rubytalk.org/t/symbols-and-strings/65710/3 "2012-06-19T16:58:47Z")
I've liked the distinction between symbols and strings since I first encountered it in LISP. Symbols to me are abstract entities which happen to be typically represented with characters, while strings are explicitly series of characters. With this perspective, it makes sense that "b" \> "a", but :b \> :a gives an error, and :a + :b gives an error. If symbols became immutable strings, this distinction would be lost. But in the end, the proof is in the code. I suspect functionally there'd not be much difference, but I'm just a beginner. > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Eric\_Christopherson](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/eric_christopherson/32/1849_2.png) [@Eric\_Christopherson](https://rubytalk.org/u/Eric_Christopherson)\ **Post date:** [19 June 2012 19:15 UTC](https://rubytalk.org/t/symbols-and-strings/65710/4 "2012-06-19T19:15:40Z")
A discussion on this just came up on Stack Overflow: > > **···** > > On Mon, Jun 18, 2012 at 5:09 PM, Hal Fulton \ wrote: > > > Hello, all... > > > > A modest proposal here... I think (tentatively) that Symbol should inherit > > from String, and a symbol should basically be an immutable string. > > > > Reply here and/or on my blog as you see fit: [http://rubyhacker.wordpress.com](http://rubyhacker.wordpress.com) > > > > Cheers, > > Hal Fulton ---
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [18 June 2012 23:00 UTC](https://rubytalk.org/t/symbols-and-strings/65710/5 "2012-06-18T23:00:43Z")
Silly of me. I not recall this at all, and even believed it was an original idea... Those who cannot remember history are condemned to Google it... Hal > **···** > > On Mon, Jun 18, 2012 at 5:31 PM, Eric Hodel \ wrote: > > > On Jun 18, 2012, at 15:09, Hal Fulton wrote: > > \> Hello, all... > > \> > > \> A modest proposal here... I think (tentatively) that Symbol should > > inherit > > \> from String, and a symbol should basically be an immutable string. > > \> > > \> Reply here and/or on my blog as you see fit: > > [http://rubyhacker.wordpress.com](http://rubyhacker.wordpress.com) > > > > This happened (see thread at [ruby-core:9188]) but was reverted. I can't > > think of the proper keywords to find the reason for the reversion. ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [19 June 2012 13:35 UTC](https://rubytalk.org/t/symbols-and-strings/65710/6 "2012-06-19T13:35:55Z")
I one has Symbol inherit String then "is a" relationship is violated. You cannot use the sub class where you can use the super class (e.g. try to append to a frozen String). See David's remark [http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-String-tp3558662p3558699.html](http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-String-tp3558662p3558699.html) Cheers robert > **···** > > On Tue, Jun 19, 2012 at 12:31 AM, Eric Hodel \ wrote: > > > This happened (see thread at [ruby-core:9188]) but was reverted. I can't think of the proper keywords to find the reason for the reversion. > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![Matthew\_Kerwin](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/matthew_kerwin/32/1845_2.png) [@Matthew\_Kerwin](https://rubytalk.org/u/Matthew_Kerwin)\ **Post date:** [19 June 2012 23:36 UTC](https://rubytalk.org/t/symbols-and-strings/65710/7 "2012-06-19T23:36:52Z")
I'm pretty sure I'm not a beginner (although programming changes so fast it's almost impossible to be old-hat in anything relevant) but I agree pretty much in whole with what you're saying. In a compiled/pre-parsed/JIT environment there \_could\_ be a dramatic difference between symbols and immutable strings – symbols could easily be replaced with some enumerator type, or integers, or even completely optimised away, depending on context. To my way of thinking symbols, when they're called symbols, are "valueless data" – their worth is in their name. Immutable strings \_do\_ contain valuable data, even if you're not allowed to modify it. (If that wasn't the case, Java would be an even harder place to get anything useful done.) By extension I'd argue that a symbol is atomic; the whole name is valuable, but no part of it is. As such an .each\_char iterator could make perfect sense for an immutable string, but not for a symbol. I always thought the :"foo" syntax was handy (for :"foo#{bar}baz" cases), but it only ever served to confuse the issue for me. Personally I tend to use String#to\_sym for those cases that I want to dynamically generate a symbol; it's an explicit cast, and provides a clear boundary between "creating the name" and then "using it". Note: it may be more or less optimal at runtime to do it this way, but I don't care; I'm after maintainability and easing my own understanding here. I should get back to work. > **···** > > On 20 June 2012 02:58, Dan Connelly \ wrote: > > > I've liked the distinction between symbols and strings since I first > > encountered it in LISP. Symbols to me are abstract entities which > > happen to be typically represented with characters, while strings are > > explicitly series of characters. With this perspective, it makes sense > > that "b" \> "a", but :b \> :a gives an error, and :a + :b gives an error. > > If symbols became immutable strings, this distinction would be lost. > > > > But in the end, the proof is in the code. I suspect functionally > > there'd not be much difference, but I'm just a beginner. > > -- > Matthew Kerwin, B.Sc (CompSci) (Hons) > [http://matthew.kerwin.net.au/](http://matthew.kerwin.net.au/) > ABN: 59-013-727-651 > > "You'll never find a programming language that frees > you from the burden of clarifying your ideas." - xkcd ---
**Author:** ![Matthew\_Kerwin](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/matthew_kerwin/32/1845_2.png) [@Matthew\_Kerwin](https://rubytalk.org/u/Matthew_Kerwin)\ **Post date:** [19 June 2012 02:52 UTC](https://rubytalk.org/t/symbols-and-strings/65710/8 "2012-06-19T02:52:12Z")
For the record, this: \<[http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-lt-String-td3558662.html>](http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-lt-String-td3558662.html>); > **···** > > On 19 June 2012 09:00, Hal Fulton \ wrote: > > > Silly of me. I not recall this at all, and even believed it was an > > original idea... > > > > Those who cannot remember history are condemned to Google it... > > > > Hal > > > > On Mon, Jun 18, 2012 at 5:31 PM, Eric Hodel \ wrote: > > > > > On Jun 18, 2012, at 15:09, Hal Fulton wrote: > > > \> Hello, all... > > > \> > > > \> A modest proposal here... I think (tentatively) that Symbol should > > > \> inherit > > > \> from String, and a symbol should basically be an immutable string. > > > \> > > > \> Reply here and/or on my blog as you see fit: > > > \> [http://rubyhacker.wordpress.com](http://rubyhacker.wordpress.com) > > > > > > This happened (see thread at [ruby-core:9188]) but was reverted. I can't > > > think of the proper keywords to find the reason for the reversion. > > -- > Matthew Kerwin, B.Sc (CompSci) (Hons) > [http://matthew.kerwin.net.au/](http://matthew.kerwin.net.au/) > ABN: 59-013-727-651 > > "You'll never find a programming language that frees > you from the burden of clarifying your ideas." - xkcd ---
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [19 June 2012 15:17 UTC](https://rubytalk.org/t/symbols-and-strings/65710/9 "2012-06-19T15:17:28Z")
Personally, I don't have a problem with "reducing the contract" of a String. Freezing an object also reduces its contract. Hal > **···** > > On Tue, Jun 19, 2012 at 8:35 AM, Robert Klemme \wrote: > > > On Tue, Jun 19, 2012 at 12:31 AM, Eric Hodel \ wrote: > > \> This happened (see thread at [ruby-core:9188]) but was reverted. I > > can't think of the proper keywords to find the reason for the reversion. > > > > I one has Symbol inherit String then "is a" relationship is violated. > > You cannot use the sub class where you can use the super class (e.g. > > try to append to a frozen String). See David's remark > > > > [http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-String-tp3558662p3558699.html](http://ruby.11.n6.nabble.com/Bikeshed-No-more-Symbol-String-tp3558662p3558699.html) > > > > Cheers > > > > robert > > > > -- > > remember.guy do |as, often| as.you\_can - without end > > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [19 June 2012 16:49 UTC](https://rubytalk.org/t/symbols-and-strings/65710/10 "2012-06-19T16:49:31Z")
> Personally, I don't have a problem with "reducing the contract" > of a String. It's just that Ruby is not particularly suited to using inheritance in different ways. In Eiffel you can do all this and do it visibly. In Ruby there's just mixing in modules and class inheritance. > Freezing an object also reduces its contract. Kind of. But I consider that a special case because freeze prevents all mutations but not other operations. It also does not restrict the range of valid state - it just freezes it. Kind regards robert > **···** > > On Tue, Jun 19, 2012 at 5:17 PM, Hal Fulton \ wrote: > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [19 June 2012 20:12 UTC](https://rubytalk.org/t/symbols-and-strings/65710/11 "2012-06-19T20:12:48Z")
> \> Freezing an object also reduces its contract. > > Kind of. But I consider that a special case because freeze prevents > all mutations but not other operations. It also does not restrict the > range of valid state - it just freezes it. Hmm. If a Symbol is-a frozen String, how does that reduce the range of valid state any more than a "real" frozen String? What operations other than mutations are prohibited? Hal ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [20 June 2012 07:12 UTC](https://rubytalk.org/t/symbols-and-strings/65710/12 "2012-06-20T07:12:52Z")
> > \> Freezing an object also reduces its contract. > > > > Kind of. But I consider that a special case because freeze prevents > > all mutations but not other operations. It also does not restrict the > > range of valid state - it just freezes it. > > Hmm. If a Symbol is-a frozen String, how does that reduce the range > of valid state any more than a "real" frozen String? Freezing does \_not\_ reduce the state, which is what I said above. With inheritance Symbol is-a String - not "frozen String". If at all the inheritance would be the other way round: a String is-a Symbol and it would extend the contract by mutating methods. > What operations > other than mutations are prohibited? For example: String has method \<\< which is part of the public contract and that will be broken by \_all\_ Symbol instances. So you give someone something and say "this is a String" but in reality it is not because all instances lack many of the functionality of String. While with actually freezing Strings \<\< works most of the time and there are just some instances which are in a state (frozen) which does not allow successful execution of the method. Kind regards robert > **···** > > On Tue, Jun 19, 2012 at 10:12 PM, Hal Fulton \ wrote: > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![Henry\_Maddocks1](https://avatars.discourse-cdn.com/v4/letter/h/ba9def/32.png) [@Henry\_Maddocks1](https://rubytalk.org/u/Henry_Maddocks1)\ **Post date:** [20 June 2012 20:42 UTC](https://rubytalk.org/t/symbols-and-strings/65710/13 "2012-06-20T20:42:23Z")
This is a very good point. String should be a sub class of Symbol. I wonder if this was considered. Henry > **···** > > On 20/06/2012, at 7:12 PM, Robert Klemme wrote: > > > If at all > > the inheritance would be the other way round: a String is-a Symbol and > > it would extend the contract by mutating methods. ---
**Author:** ![11142](https://avatars.discourse-cdn.com/v4/letter/1/e0b2c6/32.png) [@11142](https://rubytalk.org/u/11142)\ **Post date:** [20 June 2012 20:50 UTC](https://rubytalk.org/t/symbols-and-strings/65710/14 "2012-06-20T20:50:17Z")
This is an extremely bad idea. Symbol is just that – a symbol. Internally it is stored as a \*number\* and in C code passed by-value, like Fixnum, instead of by-ref, like all other objects. It is only shown as a bit of text for display. Symbols are not immutable strings, and Strings are not mutable symbols. You should not confuse the two, and they should not inherit from each other. They are extremely different entities. Think of symbols as a crossover between enums, magic numeric constants and – as the last place – strings. -- Matma Rex > **···** > > 2012/6/20 Henry Maddocks \: > > > On 20/06/2012, at 7:12 PM, Robert Klemme wrote: > > > > > If at all > > > the inheritance would be the other way round: a String is-a Symbol and > > > it would extend the contract by mutating methods. > > > > This is a very good point. String should be a sub class of Symbol. I wonder if this was considered. ---
**Author:** ![Henry\_Maddocks1](https://avatars.discourse-cdn.com/v4/letter/h/ba9def/32.png) [@Henry\_Maddocks1](https://rubytalk.org/u/Henry_Maddocks1)\ **Post date:** [20 June 2012 20:58 UTC](https://rubytalk.org/t/symbols-and-strings/65710/15 "2012-06-20T20:58:04Z")
> > > If at all > > > the inheritance would be the other way round: a String is-a Symbol and > > > it would extend the contract by mutating methods. > > > > This is a very good point. String should be a sub class of Symbol. I wonder if this was considered. > > This is an extremely bad idea. Well a lot of people, including Matz, disagree with you. > Symbol is just that – a symbol. Internally it is stored as a \*number\* > and in C code passed by-value, like Fixnum, instead of by-ref, like > all other objects. It is only shown as a bit of text for display. The internal representation is of no concern to the programmer, only it's utility. There seems to be a desire to be able to use String and Symbol interchangeably, hence this discussion. Henry > **···** > > On 21/06/2012, at 8:50 AM, Bartosz Dziewoński wrote: > > > 2012/6/20 Henry Maddocks \: > > > > > On 20/06/2012, at 7:12 PM, Robert Klemme wrote: ---
**Author:** ![11142](https://avatars.discourse-cdn.com/v4/letter/1/e0b2c6/32.png) [@11142](https://rubytalk.org/u/11142)\ **Post date:** [20 June 2012 21:17 UTC](https://rubytalk.org/t/symbols-and-strings/65710/16 "2012-06-20T21:17:16Z")
> > This is an extremely bad idea. > > Well a lot of people, including Matz, disagree with you. I'd like to see where he explicitly disagrees with this. > The internal representation is of no concern to the programmer, only it's utility. Wrong. It's as if you said that a linked list and an array are the same thing and the difference in the implementation is of no concern to the programmer, since both can support the same interface. Ruby Strings and Symbols are fundamentally different on every level (as I explained), and should be used in different contexts, for both code clarity and performance. > There seems to be a desire to be able to use String and Symbol interchangeably, hence this discussion. If Symbol and String have the same function, then one of them should probably be removed. (Except they don't, in most cases; in the few cases where they do the programmer should probably suck it up, choose one representation, stick to it and convert input data to it himself.) -- Matma Rex > **···** > > 2012/6/20 Henry Maddocks \: > > > On 21/06/2012, at 8:50 AM, Bartosz Dziewoński wrote: ---
**Author:** ![Jeremy\_Bopp](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/jeremy_bopp/32/1937_2.png) [@Jeremy\_Bopp](https://rubytalk.org/u/Jeremy_Bopp)\ **Post date:** [20 June 2012 22:06 UTC](https://rubytalk.org/t/symbols-and-strings/65710/17 "2012-06-20T22:06:27Z")
Given that Strings and Symbols are different entities (as has been discussed at length here and other places), it's not possible to expect them to be interchangeable in \*all\* cases. This even holds true if one class inherits from the other. After all, the point of descending one class from another is to make something related but at least a little different. Therefore, interchangeability must be limited to some extent as long as Symbol and String are different things. So then, in what cases would it be helpful to use them interchangeably? Is it possible to define a common, useful interface that both Symbol and String could implement. If so, perhaps a class or module could be defined for that interface and incorporated into both classes as appropriate. From what I've seen, the most frequently voiced desire is to be able to use apparently equivalent symbols and strings as fully equivalent hash keys. What else is there? -Jeremy > **···** > > On 06/20/2012 03:58 PM, Henry Maddocks wrote: > > > On 21/06/2012, at 8:50 AM, Bartosz Dziewoński wrote: > > > > > Symbol is just that – a symbol. Internally it is stored as a \*number\* > > > and in C code passed by-value, like Fixnum, instead of by-ref, like > > > all other objects. It is only shown as a bit of text for display. > > > > The internal representation is of no concern to the programmer, only it's utility. > > There seems to be a desire to be able to use String and Symbol interchangeably, hence this discussion. ---
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [20 June 2012 22:25 UTC](https://rubytalk.org/t/symbols-and-strings/65710/18 "2012-06-20T22:25:54Z")
I suppose that's the biggest area of concern for me. I do sometimes want to perform stringlike operations, e.g., on the parameter into method\_missing, but that merely requires a single to\_s. Likewise I sometimes want to add an equal sign onto a symbol in metaprogramming:     (name.to\_s \<\< "=").to\_sym Hal > **···** > > On Wed, Jun 20, 2012 at 5:06 PM, Jeremy Bopp \ wrote: > > > So then, in what cases would it be helpful to use them interchangeably? > > Is it possible to define a common, useful interface that both Symbol > > and String could implement. If so, perhaps a class or module could be > > defined for that interface and incorporated into both classes as > > appropriate. > > > > From what I've seen, the most frequently voiced desire is to be able to > > use apparently equivalent symbols and strings as fully equivalent hash > > keys. What else is there? ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [20 June 2012 22:43 UTC](https://rubytalk.org/t/symbols-and-strings/65710/19 "2012-06-20T22:43:07Z")
Even that would not be solved by inheritance because instance of different classes can never be equivalent. Kind regards robert PS: I said "If at all..." - so I am not a fan of String as subclass of Symbol either. > **···** > > On Thu, Jun 21, 2012 at 12:25 AM, Hal Fulton \ wrote: > > > On Wed, Jun 20, 2012 at 5:06 PM, Jeremy Bopp \ wrote: > > > > > So then, in what cases would it be helpful to use them interchangeably? > > > Is it possible to define a common, useful interface that both Symbol > > > and String could implement. If so, perhaps a class or module could be > > > defined for that interface and incorporated into both classes as > > > appropriate. > > > > > > From what I've seen, the most frequently voiced desire is to be able to > > > use apparently equivalent symbols and strings as fully equivalent hash > > > keys. > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![Jeremy\_Bopp](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/jeremy_bopp/32/1937_2.png) [@Jeremy\_Bopp](https://rubytalk.org/u/Jeremy_Bopp)\ **Post date:** [21 June 2012 02:10 UTC](https://rubytalk.org/t/symbols-and-strings/65710/20 "2012-06-21T02:10:42Z")
With regard to metaprogramming, perhaps the problem could be better solved by allowing the things that currently consume only symbols to also consume strings or really anything that provides a to\_sym method. That would also better follow the notion of duck typing. I'm not sure if this would help you in your particular case very much though. I haven't heard any arguments for or against such an approach before. As long as the related documentation was clear about the requirement of a to\_sym implementation that returns a Symbol instance, this wouldn't appear to be a problem right off (... he says naively...). -Jeremy > **···** > > On 06/20/2012 05:25 PM, Hal Fulton wrote: > > > On Wed, Jun 20, 2012 at 5:06 PM, Jeremy Bopp \ \\> wrote: > > > >     So then, in what cases would it be helpful to use them interchangeably? > >      Is it possible to define a common, useful interface that both Symbol > >     and String could implement. If so, perhaps a class or module could be > >     defined for that interface and incorporated into both classes as > >     appropriate. > > > >     From what I've seen, the most frequently voiced desire is to be able to > >     use apparently equivalent symbols and strings as fully equivalent hash > >     keys. What else is there? > > > > I suppose that's the biggest area of concern for me. > > > > I do sometimes want to perform stringlike operations, e.g., on the parameter > > into method\_missing, but that merely requires a single to\_s. Likewise I > > sometimes > > want to add an equal sign onto a symbol in metaprogramming: > > > >     (name.to\_s \<\< "=").to\_sym [Next page](https://rubytalk.org/t/symbols-and-strings/65710.md?page=2)