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hsutter 2015-12-23 11:32:46 -08:00
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@ -12325,7 +12325,6 @@ Don't replicate the work of others.
Benefit from other people's work when they make improvements.
Help other people when you make improvements.
**References**: ???
### <a name="Rsl-sl"></a> SL.2: Prefer the standard library to other libraries
@ -12334,10 +12333,64 @@ Help other people when you make improvements.
More people know the standard library.
It is more likely to be stable, well-maintained, and widely available than your own code or most other libraries.
## SL.con: Containers
* [SL.10: Prefer using STL `array` or `vector` instead of a C array](#Rsl-arrays)
* [SL.11: Prefer using STL `vector` by default unless you have a reason to use a different container](#Rsl-vector)
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### <a name="Rsl-arrays"></a> SL.10: Prefer using STL `array` or `vector` instead of a C array
##### Reason
C arrays are less safe, and have no advantages over `array` and `vector`.
For a fixed-length array, use `std::array`, which does not degenerate to a pointer when passed to a function and does know its size.
For a variable-length array, use `std::vector`, which additionally can change its size and handles memory allocation.
##### Example
int v[SIZE]; // BAD
std::array<int,SIZE> w; // ok
##### Example
int* v = new int[initial_size]; // BAD, owning raw pointer
delete[] v; // BAD, manual delete
std::vector<int> w(initial_size); // ok
##### Enforcement
* Flag declaration of a C array inside a function or class that also declares an STL container (to avoid excessive noisy warnings on legacy non-STL code). To fix: At least change the C array to a `std::array`.
### <a name="Rsl-vector"></a> SL.11: Prefer using STL `vector` by default unless you have a reason to use a different container
##### Reason
`vector` and `array` are the only standard containers that offer the fastest general-purpose access (random access, including being vectorization-friendly), the fastest default access pattern (begin-to-end or end-to-begin is prefetcher-friendly), and the lowest space overhead (contiguous layout has zero per-element overhead, which is cache-friendly). Usually you need to add and remove elements from the container, so use `vector` by default; if you don't need to modify the container's size, use `array`.
Even when other containers seem more suited, such a `map` for O(log N) lookup performance or a `list` for efficient insertion in the middle, a `vector` will usually still perform better for containers up to a few KB in size.
##### Note
`string` should not be used as a container of individual characters. A `string` is a textual string; if you want a container of characters, use `vector</*char_type*/>` or `array</*char_type*/>` instead.
##### Exceptions
If you have a good reason to use another container, use that instead. For example:
* If `vector` suits your needs but you don't need the container to be variable size, use `array` instead.
* If you want a dictionary-style lookup container that guarantees O(K) or O(log N) lookups, the container will be larger (more than a few KB) and you perform frequent inserts so that the overhead of maintaining a sorted `vector` is infeasible, go ahead and use an `unordered_map` or `map` instead.
##### Enforcement
* Flag a `vector` whose size never changes after construction (such as because it's `const` or because no non-`const` functions are called on it). To fix: Use an `array` instead.
## SL.str: String
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