explicit

A set of small tools that allow you to state your intentions more explicitly in the interfaces.

Tool out_param

A tool for indicating function output parameters in call sites:

void clear(out_param<std::string&> s) // output parameter in function declaration
{
    s.get().clear();
}

std::string s {"text"};
clear(out(s));                        // in function invokation

For more, see here.

Tool tagged_bool

An alternative to type bool in function arguments. It allows to associate a name with the boolean type. No nasty implicit converisons from/to int, double, or pointers. Different instantiations of tagged_bool are not interconvertible:

class EngineStartedTag_; // never defined
class CrewReadyTag_;     // never defined

using EngineStarted = tagged_bool<EngineStartedTag_>; // one boolean type
using CrewReady     = tagged_bool<CrewReadyTag_>;     // another boolean type

void set_status(EngineStarted started, CrewReady ready); // function declaration
set_status(EngineStarted{true}, CrewReady{true});        // function invokation

For more, see here.

Tool only_when

A tool for disabling some unwanted implicit conversions to types present in your function signatures. For instance, you may want your function to take a filesystem::path but not allow an implicit conversion from std::string:

using only_path = only_when<filesystem::path, is_a_non_string>; // you define type trait is_a_non_string
void process(only_path p);  // function declaration
process(path);    // ok
process(string);  // error

For more, see here.

Tool only_int

An alternative to type int in function arguments. It binds to ints and int proxies but not to double:

void scale(only_int i); // declaration
scale(2);     // ok
scale(2.5);   // error

For more, see here.

Tool lvalue_ref

This allows the constructor parameters to bind to lvalues, but not to rvalues:

struct Processor
{
  Big const& _big;
  explicit Processor(lvalue_ref<const Big> b) : _big(b) {}
};

const Big b {};
Processor p {b}; // ok
Processor q {Big{}}; // error (temporary)

For more, see here.

Tool not_null

This allows to indicate in function interface that a passed pointer is assumed never to be null:

void process(not_null<i*> p); // function declaration
int i = 0;
process(&i);                  // error: no implicit conversion to not_null
process(as_not_null(&i));     // ok: explicit adjustment

For more, see here.

installation

It is a C++11 header-only library.

All library components are defined in namespace ak_toolkit::xplicit. However, including header <ak_toolkit/namespace_xpl> introduces a shorter alias xpl. Using xpl is shorter, but risks clashes in case a different library also uses short xpl for some other purpose. If that happens, you have to go with the longer but safer version.

License

Distributed under the Boost Software License, Version 1.0.

Acknowledgements

The idea of the generalized only_when was proposed by Vicente J. Botet Escriba. Tomasz Kamiński suggested the support for std::reference_wrapper in rvalue_ref.