SGIextensions(3cxx)

📦

version 14-20240412 · 16 versions

🎀 NAME 🎀

okay so this is the SGIextensions(3cxx) page — part 1, bestie — and the NAME line is literally:

SGIextensions — SGI

short, sweet, iconic.

✨ SYNOPSIS ✨

this is the whole cast, no cap. every class and function is right here, with the exact signatures because we do not play about details 💅

💖 Classes 💖

class __gnu_cxx::binary_compose< _Operation1, _Operation2, _Operation3 > — An SGI extension .
struct __gnu_cxx::constant_binary_fun< _Result, _Arg1, _Arg2 > — An SGI extension .
struct __gnu_cxx::constant_unary_fun< _Result, _Argument > — An SGI extension .
struct __gnu_cxx::constant_void_fun< _Result > — An SGI extension .
class __gnu_cxx::hash_map< _Key, _Tp, _HashFn, _EqualKey, _Alloc >
class __gnu_cxx::hash_multimap< _Key, _Tp, _HashFn, _EqualKey, _Alloc >
class __gnu_cxx::hash_multiset< _Value, _HashFcn, _EqualKey, _Alloc >
class __gnu_cxx::hash_set< _Value, _HashFcn, _EqualKey, _Alloc >
struct __gnu_cxx::project1st< _Arg1, _Arg2 > — An SGI extension .
struct __gnu_cxx::project2nd< _Arg1, _Arg2 > — An SGI extension .
struct __gnu_cxx::rb_tree< _Key, _Value, _KeyOfValue, _Compare, _Alloc >
class __gnu_cxx::rope< _CharT, _Alloc >
struct __gnu_cxx::select1st< _Pair > — An SGI extension .
struct __gnu_cxx::select2nd< _Pair > — An SGI extension .
class __gnu_cxx::slist< _Tp, _Alloc >
class __gnu_cxx::subtractive_rng
struct __gnu_cxx::temporary_buffer< _ForwardIterator, _Tp >
class __gnu_cxx::unary_compose< _Operation1, _Operation2 > — An SGI extension .

🌈 Functions 🌈

template<typename _Tp > const _Tp & __gnu_cxx::__median (const _Tp &__a, const _Tp &__b, const _Tp &__c) — Find the median of three values.
template<typename _Tp , typename _Compare > const _Tp & __gnu_cxx::__median (const _Tp &__a, const _Tp &__b, const _Tp &__c, _Compare __comp) — Find the median of three values using a predicate for comparison.
constexpr size_t std::bitset< _Nb >::_Find_first () const noexcept — Finds the index of the first 'on' bit.
constexpr size_t std::bitset< _Nb >::_Find_next (size_t __prev) const noexcept — Finds the index of the next 'on' bit after prev.
template<class _Operation1 , class _Operation2 > unary_compose< _Operation1, _Operation2 > __gnu_cxx::compose1 (const _Operation1 &__fn1, const _Operation2 &__fn2) — An SGI extension .
template<class _Operation1 , class _Operation2 , class _Operation3 > binary_compose< _Operation1, _Operation2, _Operation3 > __gnu_cxx::compose2 (const _Operation1 &__fn1, const _Operation2 &__fn2, const _Operation3 &__fn3) — An SGI extension .
template<class _Result > constant_void_fun< _Result > __gnu_cxx::constant0 (const _Result &__val) — An SGI extension .
template<class _Result > constant_unary_fun< _Result, _Result > __gnu_cxx::constant1 (const _Result &__val) — An SGI extension .
template<class _Result > constant_binary_fun< _Result, _Result, _Result > __gnu_cxx::constant2 (const _Result &__val) — An SGI extension .
template<typename _InputIterator , typename _Size , typename _OutputIterator > std::pair< _InputIterator, _OutputIterator > __gnu_cxx::copy_n (_InputIterator __first, _Size __count, _OutputIterator __result) — Copies the range [first,first+count) into [result,result+count).
template<typename _InputIterator , typename _Distance > void __gnu_cxx::distance (_InputIterator __first, _InputIterator __last, _Distance &__n)
template<class _Tp > _Tp __gnu_cxx::identity_element (std::multiplies< _Tp >) — An SGI extension .
template<class _Tp > _Tp __gnu_cxx::identity_element (std::plus< _Tp >) — An SGI extension .
template<typename _InputIterator1 , typename _InputIterator2 > int __gnu_cxx::lexicographical_compare_3way (_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2) — memcmp on steroids.
template<typename _Tp , typename _Integer > _Tp __gnu_cxx::power (_Tp __x, _Integer __n)
template<typename _Tp , typename _Integer , typename _MonoidOperation > _Tp __gnu_cxx::power (_Tp __x, _Integer __n, _MonoidOperation __monoid_op)
template<typename _InputIterator , typename _RandomAccessIterator > _RandomAccessIterator __gnu_cxx::random_sample (_InputIterator __first, _InputIterator __last, _RandomAccessIterator __out_first, _RandomAccessIterator __out_last)
template<typename _InputIterator , typename _RandomAccessIterator , typename _RandomNumberGenerator > _RandomAccessIterator __gnu_cxx::random_sample (_InputIterator __first, _InputIterator __last, _RandomAccessIterator __out_first, _RandomAccessIterator __out_last, _RandomNumberGenerator &__rand)
template<typename _ForwardIterator , typename _OutputIterator , typename _Distance > _OutputIterator __gnu_cxx::random_sample_n (_ForwardIterator __first, _ForwardIterator __last, _OutputIterator __out, const _Distance __n)
template<typename _ForwardIterator , typename _OutputIterator , typename _Distance , typename _RandomNumberGenerator > _OutputIterator __gnu_cxx::random_sample_n (_ForwardIterator __first, _ForwardIterator __last, _OutputIterator __out, const _Distance __n, _RandomNumberGenerator &__rand)
template<typename _InputIter , typename _Size , typename _ForwardIter > std::pair< _InputIter, _ForwardIter > __gnu_cxx::uninitialized_copy_n (_InputIter __first, _Size __count, _ForwardIter __result) — Copies the range [first,last) into result.
constexpr bitset< _Nb > & std::bitset< _Nb >::_Unchecked_set (size_t __pos) noexcept
constexpr bitset< _Nb > & std::bitset< _Nb >::_Unchecked_set (size_t __pos, int __val) noexcept
constexpr bitset< _Nb > & std::bitset< _Nb >::_Unchecked_reset (size_t __pos) noexcept
constexpr bitset< _Nb > & std::bitset< _Nb >::_Unchecked_flip (size_t __pos) noexcept
constexpr bool std::bitset< _Nb >::_Unchecked_test (size_t __pos) const noexcept

🦋 Detailed Description 🦋

so here's the lore, bestie 💖 because libstdc++ based its implementation of the STL subsections of the library on the SGI 3.3 implementation, we inherited their extensions as well. slay, but also: that's where these guys come from.

they are additionally documented in the online documentation, a copy of which is also shipped with the library source code (in .../docs/html/documentation.html). You can also read the documentation on SGI's site, which is still running even though the code is not maintained. iconic but also kind of haunted 💀

NB that the following notes are pulled from various comments all over the place, so they may seem stilted.

The identity_element functions are not part of the C++ standard; SGI provided them as an extension. Its argument is an operation, and its return value is the identity element for that operation. It is overloaded for addition and multiplication, and you can overload it for your own nefarious operations. nefarious operations?? we love to see it 😭

As an extension to the binders, SGI provided composition functors and wrapper functions to aid in their creation. The unary_compose functor is constructed from two functions/functors, f and g. Calling operator() with a single argument x returns f(g(x)). The function compose1 takes the two functions and constructs a unary_compose variable for you.

binary_compose is constructed from three functors, f, g1, and g2. Its operator() returns f(g1(x),g2(x)). The function compose2 takes f, g1, and g2, and constructs the binary_compose instance for you. For example, if f returns an int, then

int answer = (compose2(f,g1,g2))(x);

is equivalent to

int temp1 = g1(x);
int temp2 = g2(x);
int answer = f(temp1,temp2);

But the first form is more compact, and can be passed around as a functor to other algorithms. compact king behavior fr fr ✨

As an extension, SGI provided a functor called identity. When a functor is required but no operations are desired, this can be used as a pass-through. Its operator() returns its argument unchanged.

select1st and select2nd are extensions provided by SGI. Their operator()s take a std::pair as an argument, and return either the first member or the second member, respectively. They can be used (especially with the composition functors) to strip data from a sequence before performing the remainder of an algorithm. the way they just. grab the data. love that for us 🫶

The operator() of the project1st functor takes two arbitrary arguments and returns the first one, while project2nd returns the second one. They are extensions provided by SGI.

These three functors are each constructed from a single arbitrary variable/value. Later, their operator()s completely ignore any arguments passed, and return the stored value.

constant_void_fun's operator() takes no arguments
constant_unary_fun's operator() takes one argument (ignored)
constant_binary_fun's operator() takes two arguments (ignored)

The helper creator functions constant0, constant1, and constant2 each take a result argument and construct variables of the appropriate functor type.

🧩 Function Documentation 🧩

💫 `__gnu_cxx::__median`

template<typename _Tp > const _Tp & __gnu_cxx::__median (const _Tp & __a,
    const _Tp & __b, const _Tp & __c)

Find the median of three values. That's it, that's the whole job, bestie is out here picking the middle child 💅

Parameters:

__a — a value.
__b — a value.
__c — a value.

Returns: one of a, b or c.

Okay so the actual tea ☕: if {l,m,n} is some convolution of {a,b,c} such that l<=m<=n then the value returned will be m. This is an SGI extension. ✨

💫 `__gnu_cxx::__median` (with a predicate)

template<typename _Tp , typename _Compare > const _Tp & __gnu_cxx::__median
    (const _Tp & __a, const _Tp & __b, const _Tp & __c, _Compare __comp)

Find the median of three values using a predicate for comparison. Same energy, but now you decide what "middle" means 🎀

Parameters:

__a — a value.
__b — a value.
__c — a value.
__comp — a binary predicate.

Returns: one of a, b or c.

The rule: if {l,m,n} is some convolution of {a,b,c} such that comp(l,m) and comp(m,n) are both true, then the value returned will be m. This is an SGI extension. 🌸

🔎 `std::bitset<_Nb>::_Find_first`

template<size_t _Nb> constexpr size_t std::bitset< _Nb >::_Find_first ()
    const [inline],  [constexpr],  [noexcept]

Finds the index of the first 'on' bit. Cute little scout, going first 🔥

Returns: the index of the first bit set, or size() if not found. 😭 (yes, it returns size(), not a sad little -1)

See also: _Find_next

🔎 `std::bitset<_Nb>::_Find_next`

template<size_t _Nb> constexpr size_t std::bitset< _Nb >::_Find_next (size_t
    __prev) const [inline],  [constexpr],  [noexcept]

Finds the index of the next 'on' bit after prev. The sequel, the second act, the follow-up single 💅

Returns: the index of the next bit set, or size() if not found.

Parameters:

__prev — where to start searching.

See also: _Find_first