https://stackoverflow.com/questions/1838170/
"In Python 3.3 and above, the internal representation of the string will depend on the string, and can be any of latin-1, UCS-2 or UCS-4, as described in PEP 393."
Article also says PHP has immutable strings. They are mutable, although often copied.
Article also claims majority of popular languages have immutable strings.
As well as the ones listed there is also PHP and Rust (and C, but they did say C++ - and obviously Ruby since that's the subject of the article).
I'm also a bit surprised by the last sentence.
"However, if you do measure a negative performance impact, there is no doubt you are measuring incorrectly."
There must surely be programs doing a lot of string building or in-place modification that would benefit from non-frozen.
Python strings aren’t even proper Unicode strings. They’re sequences of code points rather than scalar values, meaning they can contain surrogates. This is incompatible with basically everything: UTF-* as used by sensible things, and unvalidated UTF-16 as used in the likes of JavaScript, Windows wide strings and Qt.
In C, C++, and Rust, the question of "are strings in this language mutable or immutable?" isn't applicable, because those languages have transitive mutability qualifiers. So they only need a single string type, and whether you can mutate it or not depends on context. (C++ and Rust have multiple string types, but the differences among them aren't about mutability.) In languages without this feature, a given value is either always mutable or never mutable, and so it's necessary to pick one or the other for string literals.
Sure, that doesn't change the point that mutable strings are a thing in those languages. And I don't think C's const is really a "mutability qualifier" - certainly not a very effective one at any rate.
It's perfectly fine to have mutable strings in a hash table; just document that the behavior becomes unspecified if keys are mutated while they are in the table.
Make sure the behavior is safe: it won't crash or be exploitable by a remote attacker.
It works especially well in a language that doesn't emphasize mutation; i.e. you don't reach for string mutation as your go-to tool for manipulation.
Explicit "freeze" stuff is an awful thing to foist onto the programmer.
The copy-and-freeze behavior is a special case that applies only to strings, presumably because the alternative was too much of a footgun since programmers usually think of strings in terms of value semantics.
I don't think anyone likes the explicit .freeze calls everywhere; I think the case for frozen strings in Ruby is primarily based on performance rather than correctness (which is why it wasn't obvious earlier in the language's history that it was the right call), and the reason it's hard to make the default is because of compatibility.
Article claims python 3 uses UTF-8.
https://stackoverflow.com/questions/1838170/ "In Python 3.3 and above, the internal representation of the string will depend on the string, and can be any of latin-1, UCS-2 or UCS-4, as described in PEP 393."
Article also says PHP has immutable strings. They are mutable, although often copied.
Article also claims majority of popular languages have immutable strings. As well as the ones listed there is also PHP and Rust (and C, but they did say C++ - and obviously Ruby since that's the subject of the article).
I'm also a bit surprised by the last sentence. "However, if you do measure a negative performance impact, there is no doubt you are measuring incorrectly." There must surely be programs doing a lot of string building or in-place modification that would benefit from non-frozen.
Python strings aren’t even proper Unicode strings. They’re sequences of code points rather than scalar values, meaning they can contain surrogates. This is incompatible with basically everything: UTF-* as used by sensible things, and unvalidated UTF-16 as used in the likes of JavaScript, Windows wide strings and Qt.
In C, C++, and Rust, the question of "are strings in this language mutable or immutable?" isn't applicable, because those languages have transitive mutability qualifiers. So they only need a single string type, and whether you can mutate it or not depends on context. (C++ and Rust have multiple string types, but the differences among them aren't about mutability.) In languages without this feature, a given value is either always mutable or never mutable, and so it's necessary to pick one or the other for string literals.
Sure, that doesn't change the point that mutable strings are a thing in those languages. And I don't think C's const is really a "mutability qualifier" - certainly not a very effective one at any rate.
Important information omitted from title: this is for the Ruby language.
It's perfectly fine to have mutable strings in a hash table; just document that the behavior becomes unspecified if keys are mutated while they are in the table.
Make sure the behavior is safe: it won't crash or be exploitable by a remote attacker.
It works especially well in a language that doesn't emphasize mutation; i.e. you don't reach for string mutation as your go-to tool for manipulation.
Explicit "freeze" stuff is an awful thing to foist onto the programmer.
In general, Ruby does allow mutable values in hash tables, with basically those semantics: https://docs.ruby-lang.org/en/3.4/Hash.html#class-Hash-label...
The copy-and-freeze behavior is a special case that applies only to strings, presumably because the alternative was too much of a footgun since programmers usually think of strings in terms of value semantics.
I don't think anyone likes the explicit .freeze calls everywhere; I think the case for frozen strings in Ruby is primarily based on performance rather than correctness (which is why it wasn't obvious earlier in the language's history that it was the right call), and the reason it's hard to make the default is because of compatibility.
> since programmers usually think of strings in terms of value semantics.
Can you blame them, when you out of your way to immerse strings in the stateful OOP paradigm, with idioms like "foo".upcase!
If you give programmers mainly a functional library for string manipulations that returns new values, then that's what they will use.