FBB::TypeTrait(3bobcat)

📦
version 6.15.01 · 7 versions
, in ubuntu stonking

🎀 NAME 🎀

FBB::TypeTrait — the type trait class, bestie 💖 (from the bobcat manual, section 3bobcat if you're keeping score)

✨ SYNOPSIS ✨

#include <bobcat/typetrait>

🦋 DESCRIPTION 🦋

okay so FBB::TypeTrait is a traits class. And when I say traits class I mean it has zero member functions and zero data members — it's literally just types hanging out in there. That's the whole point. It's giving "I'm not like the other classes" energy 💅

What's it for? Determining the basic type and other characteristics of:

  • (const) plain types
  • (const) pointer types
  • (const) reference types

It was designed after Alexandrescu's (2001) TypeTraits template class. (Yes, we're citing sources. Academic icon behavior 👑)

The FBB::LpromotesR class template is the one that figures out, at compile time, whether its second (right-hand side) template type can be promoted to its first (left-hand side) template type.

And then there's FBB::Use, which is a class template expecting two typenames LHS and RHS. It spells typename Use<LHS, RHS>::type as LHS if RHS can be promoted to LHS — or, plot twist, it spells typename Use<LHS, RHS>::type as RHS instead. Situation resolved at compile time, no runtime drama 💅

🌈 NAMESPACE 🌈

FBB

Every constructor, member, operator and manipulator mentioned in this man-page lives in the namespace FBB. All of them. No strays, no cap.

🙈 INHERITS FROM 🙈

-

(nothing. it inherits from nothing. it owes nothing to its ancestors. main character energy fr fr ✨)

👑 TypeTrait<TYPE> 👑

TYPE is the template type parameter whose characteristics need to be determined. So basically you hand it a type and it tells you what's tea 🍵

TypeTrait<TYPE> defines the type Plain — that's the plain type, aka the type with all the const / pointer / reference indication stripped off. Works for any const or non-const plain, pointer, lvalue-reference or rvalue-reference type. It just gets them all. Slay.

TypeTrait<TYPE> also defines the following bool values:

  • isClass — true if the template type argument represents a class (struct) type, false otherwise.
  • isConst — true if the template type argument represents a const type, false otherwise.
  • isPointer — true if the template type argument represents a pointer type, false otherwise.
  • isR_Ref — true if the template type argument represents an rvalue reference type, false otherwise.
  • isRef — true if the template type argument represents an lvalue reference type, false otherwise.

🌟 LpromotesR<LeftType, RightType> 🌟

LpromotesR<LeftType, RightType> defines the enum constant yes as 1 if a RightType argument can be promoted to a LeftType value or object. 💖

But bestie — the enum value yes is defined as 0 if no such constructor is available, or if such a constructor is defined using the explicit keyword. Yes, explicit ruins the promotion. We've all been there 😭

🔥 EXAMPLES 🔥

here's an example using LpromotesR, and the comments tell you exactly which answer comes out:

int main()
{
    cout << "string promotes char const *: " <<
            LpromotesR<string, char const *>::yes << '\n';  // 1
    cout << "string promotes string " <<
            LpromotesR<string, string>::yes << '\n';        // 1
    cout << "char const * promotes string " <<
            LpromotesR<char const *, string>::yes << '\n';  // 0
}

see how string promotes to char const * and to string, but char const * does NOT promote to string? that's the 0 right there. it's giving directionality. iykyk 💅

🌸 FILES 🌸

  • bobcat/typetrait — defines the class interface

🫶 SEE ALSO 🫶

  • bobcat(7)
  • Alexandrescu A. (2001) Modern C++ Design, Addison-Wesley, Boston.

💀 BUGS 💀

None Reported.

(not me being suspicious of a bug section that says nothing... but okay, we respect it 🙈)

⭐ BOBCAT PROJECT FILES ⭐

Debian Bobcat project files:

  • libbobcat6: debian package containing the shared library, changelog and copyright note;
  • libbobcat-dev: debian package containing the static library, headers, manual pages, and developer info;

🧚 BOBCAT 🧚

Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’. 🎀

This is free software, distributed under the terms of the GNU General Public License (GPL).

🍓 AUTHOR 🍓

Frank B. Brokken (f.b.brokken@rug.nl).

and that's the whole page, bestie 🫶 this one shipped in libbobcat-dev_6.15.01, dated 2005-2026, and yes it really is called FBB::TypeTrait(3bobcat) — go check it, go read it, go use it. mwah 💋

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