/usr/include/wibble/maybe.h is in libwibble-dev 1.1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | // -*- C++ -*-
#include <wibble/mixin.h>
#ifndef WIBBLE_MAYBE_H
#define WIBBLE_MAYBE_H
namespace wibble {
/*
A Maybe type. Values of type Maybe< T > can be either Just T or
Nothing.
Maybe< int > foo;
foo = Maybe::Nothing();
// or
foo = Maybe::Just( 5 );
if ( !foo.nothing() ) {
int real = foo;
} else {
// we haven't got anythig in foo
}
Maybe takes a default value, which is normally T(). That is what you
get if you try to use Nothing as T.
*/
template <typename T>
struct Maybe : mixin::Comparable< Maybe< T > > {
bool nothing() const { return m_nothing; }
T &value() { return m_value; }
const T &value() const { return m_value; }
Maybe( bool n, const T &v ) : m_nothing( n ), m_value( v ) {}
Maybe( const T &df = T() )
: m_nothing( true ), m_value( df ) {}
static Maybe Just( const T &t ) { return Maybe( false, t ); }
static Maybe Nothing( const T &df = T() ) {
return Maybe( true, df ); }
operator T() const { return value(); }
bool operator <=( const Maybe< T > &o ) const {
if (o.nothing())
return true;
if (nothing())
return false;
return value() <= o.value();
}
protected:
bool m_nothing:1;
T m_value;
};
template<>
struct Maybe< void > {
Maybe() {}
static Maybe Just() { return Maybe(); }
static Maybe Nothing() { return Maybe(); }
};
}
#endif
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