Shot in foot

[Duthomhas]

Stupid std::replace() takes references. (And, conveniently, std::min() and std::max() also work over references.)

Always remember to make yourself something that can't be changed when you aren't looking. (Because const only means it if it wants to.)

// Evil code:
replace( xs.begin(),  xs.end(),  max( xs[a], xs[b] ),  min( xs[a], xs[b] ) );

// Less evil code:
int xs_a = min( xs[a], xs[b] );  // (Yep. This was over integers.)
int xs_b = max( xs[a], xs[b] );
replace( xs.begin(), xs.end(), xs_b, xs_a );

Took me half an hour to figure out why my Kruskal MST wasn't working.
:@

[LB]

const should be renamed readonlyfromthisparticularvariable but programmers are too lazy to type that out.

Also, there's nothing wrong with the behavior of those functions - what if you really did want references to be used and didn't want to deal with the overhead/hassle of a std::reference_wrapper? Copies of primitives are cheap, whereas wrapper classes are not.

[Duthomhas]

Yes, of course. Only it's easy to forget stuff when you're playing with integers.

(The problem was that my head expected min() and max() to return copies of the integers.)

[MiiNiPaa]

Casting to non-reference type helps too:

replace( xs.begin(),  xs.end(),  static_cast<int>(max( xs[a], xs[b] )),  min( xs[a], xs[b] ) );
replace( xs.begin(),  xs.end(),  int(max( xs[a], xs[b] )),  min( xs[a], xs[b] ) );