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C+ Standard Template Library is the best designed part of C++ library. It was designed by Alexander Stepanov. https://en.wikipedia.org/wiki/Alexander_Stepanov

C+ Standard Template Library is the best designed part of C++ library. It was designed by Alexander Stepanov. https://en.wikipedia.org/wiki/Alexander_Stepanov https://en.wikipedia.org/wiki/Alexander_Stepanov

pjmlp 5mo ago
Nowadays also used by many of us (wrongly) to refer to the overall C++ standard library, instead of what was inherited from C.
tialaramex 5mo ago
So, a few things (aside from the whole nomenclature argument already in another reply) 1. Stepanov's generic programming is a good idea. Every language you've seen with "generics" that's his idea, to the extent "The STL" is generic programming, everybody agreed it's a good idea. 2. But the STL is very old now, so while the idea is good, this is one of the oldest (Stepanov had tried this in other languages before C++) implementations and so other implementations are often better, because they've learned from experience 3. As well as pretty good generic algorithms, the STL also provides a lot of container types (what Rust would call collection types) and these vary not between "excellent" and "mediocre" but between "mediocre" and "inexplicably terrifying". The most charitable explanation is that they're just intended for teaching. If you teach DS&A to a Computer Science class you want the Extrusive Doubly Linked List to teach in class. If you write software you almost certainly never need this type, but it's front an centre in the C++ STL. There's a single "I guess I would use this" container type, std::vector. It has an insane special case for bool, because WG21 are idiots, but it's otherwise a good enough growable array type and it's not worth building your own instead given the constraints. Everything else is silly, or bad, or both. std::unordered_map feels like a hash table I made in class in the mid 1990s, but it's actually the provided standard hash table container in C++ 11 onwards. std::list is just that extrusive linked list for some insane reason. The Microsoft standard library maintainer STL could not offer me any justification for what std::deque is actually supposed to be for.
- einpoklum 5mo ago
  > There's a single "I guess I would use this" container type, std::vector. About that one... I would claim that in a majority of cases where an std::vector is used, what the author really wanted was a similar type, but whose size and capacity are fixed on construction and never change. The standard C++ library does not offer such a type - so people use vector because it's handy. Agree with your takes on most of the containers. I also dislike how optionals are never used with containers as they were standardized later (and even then, problematically w.r.t. references). Thus, for example, if I lookup an object in a map of T's, the result should IMNSHO be an optional reference to a T.
  - afdbcreid 5mo ago
    What operations could such frozen vector offer that std::vector does not? If there are none, it doesn't need a separate data structure.
    - einpoklum 5mo ago
      Oh, on the contrary, the separate structure is needed and useful because it offers _less_, not more: * APIs/function signatures explain more clearly what are the intended uses of the structure that's passed. * More potential for compiler optimization * Some potential for having these on the stack (if the compiler deduces the size already at compile-time) * More convenient for static analysis * No plethora of confusing constructors (including the infernal two-element ctors which can be misinterpreted super-easily) etc.
      - nemetroid 5mo ago
        How are any of these achieved by a vector-like type with capacity frozen at construction time?
    - quuxplusone 5mo ago
      The reason I'd want "frozen-size vector" is to replace pairs of data members of the form `T* foos; size_t foos_len;` without paying another 8 bytes to store a useless capacity that's never going to change. But I don't think that makes such a container worth adding to the STL. So far, it hasn't even been worth writing in our own code. But that's the reason I've thought about writing it.
einpoklum 5mo ago
It has some very useful principles, but also some super-annoying gaffes and mis-design aspects. One example: Allocators. What a mess! Or the fact that if a map lookup fails, an exception is thrown. I can't count the times I've had some app just bail out on me with an at() exception, because the author neglected to handle it (and the map/unordered map interface did not force them to). That does not detract from Stepanov's important work.
- ahartmetz 5mo ago
  The kind of programmer who don't check (or think through so that they can't fail) their map lookups is also the kind of programmer who don't bother with const. What a non-const unchecked map lookup gives you is a default-constructed value that has just been inserted for the only reason that operator[] returns a reference, which must "point" to something. That's bad and can be confusing, but it doesn't crash. I see that problem much more often than crashes due to unchecked map lookups in production, which are very rare for me. Less than once a year.

pjmlp 5mo ago

Nowadays also used by many of us (wrongly) to refer to the overall C++ standard library, instead of what was inherited from C.

tialaramex 5mo ago

So, a few things (aside from the whole nomenclature argument already in another reply) 1. Stepanov's generic programming is a good idea. Every language you've seen with "generics" that's his idea, to the extent "The STL" is generic programming, everybody agreed it's a good idea. 2. But the STL is very old now, so while the idea is good, this is one of the oldest (Stepanov had tried this in other languages before C++) implementations and so other implementations are often better, because they've learned from experience 3. As well as pretty good generic algorithms, the STL also provides a lot of container types (what Rust would call collection types) and these vary not between "excellent" and "mediocre" but between "mediocre" and "inexplicably terrifying". The most charitable explanation is that they're just intended for teaching. If you teach DS&A to a Computer Science class you want the Extrusive Doubly Linked List to teach in class. If you write software you almost certainly never need this type, but it's front an centre in the C++ STL. There's a single "I guess I would use this" container type, std::vector. It has an insane special case for bool, because WG21 are idiots, but it's otherwise a good enough growable array type and it's not worth building your own instead given the constraints. Everything else is silly, or bad, or both. std::unordered_map feels like a hash table I made in class in the mid 1990s, but it's actually the provided standard hash table container in C++ 11 onwards. std::list is just that extrusive linked list for some insane reason. The Microsoft standard library maintainer STL could not offer me any justification for what std::deque is actually supposed to be for.

einpoklum 5mo ago
> There's a single "I guess I would use this" container type, std::vector. About that one... I would claim that in a majority of cases where an std::vector is used, what the author really wanted was a similar type, but whose size and capacity are fixed on construction and never change. The standard C++ library does not offer such a type - so people use vector because it's handy. Agree with your takes on most of the containers. I also dislike how optionals are never used with containers as they were standardized later (and even then, problematically w.r.t. references). Thus, for example, if I lookup an object in a map of T's, the result should IMNSHO be an optional reference to a T.
- afdbcreid 5mo ago
  What operations could such frozen vector offer that std::vector does not? If there are none, it doesn't need a separate data structure.
  - einpoklum 5mo ago
    Oh, on the contrary, the separate structure is needed and useful because it offers _less_, not more: * APIs/function signatures explain more clearly what are the intended uses of the structure that's passed. * More potential for compiler optimization * Some potential for having these on the stack (if the compiler deduces the size already at compile-time) * More convenient for static analysis * No plethora of confusing constructors (including the infernal two-element ctors which can be misinterpreted super-easily) etc.
    - nemetroid 5mo ago
      How are any of these achieved by a vector-like type with capacity frozen at construction time?
  - quuxplusone 5mo ago
    The reason I'd want "frozen-size vector" is to replace pairs of data members of the form `T* foos; size_t foos_len;` without paying another 8 bytes to store a useless capacity that's never going to change. But I don't think that makes such a container worth adding to the STL. So far, it hasn't even been worth writing in our own code. But that's the reason I've thought about writing it.

einpoklum 5mo ago

It has some very useful principles, but also some super-annoying gaffes and mis-design aspects. One example: Allocators. What a mess! Or the fact that if a map lookup fails, an exception is thrown. I can't count the times I've had some app just bail out on me with an at() exception, because the author neglected to handle it (and the map/unordered map interface did not force them to). That does not detract from Stepanov's important work.

ahartmetz 5mo ago
The kind of programmer who don't check (or think through so that they can't fail) their map lookups is also the kind of programmer who don't bother with const. What a non-const unchecked map lookup gives you is a default-constructed value that has just been inserted for the only reason that operator[] returns a reference, which must "point" to something. That's bad and can be confusing, but it doesn't crash. I see that problem much more often than crashes due to unchecked map lookups in production, which are very rare for me. Less than once a year.