Re: [Boost-users] [multi_index] modify_range?

Joaquín Mª López Muñoz wrote:

Jeff Flinn ha escrito:

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JOAQUIN LOPEZ MU?Z wrote:

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There is a problem, though: consider the following:

// buggy call ro modify_range modify_range(m,m.begin(),m.end(),adder(2));

What's the problem with this? Well, after *increasing* the value of an element, this is repositioned further to the end of the container, and consequentely modify_range will visit it again and engage in a neverending loop (modulo overflows.)

Would modifying a non_key(or non_derived_key dependency) ever cause repositioning?

I'm not sure if you mean this, but modifying a part of an object from which no

key extractor depends results in no repositioning. For instance

struct element{ int x,y,z };

typedef multi_index_container< element, indexed_by< ordered_unique, ordered_non_unique,

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multi_index_t;

modifying element::z in the example above does not cause repositioning ever. Is this what you were referring to?

Yes, that's what I was referring to. So in the above case, there's no need for the 'stable' version.

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// calling modify_unstable_range is now OK modify_unstable_range(m,m.begin(),m.end(),adder(2));

Doesn't this actually provide modify_key_range functionality?

No, to provide such functionality just replace the occurences of .modify(...) with .modify_key(...);

So wouldn't the only use of modify_unstable_range be for modifying keys and indirect members? So only a single modify_unstable_range calling .modify_key would suffice? Just thinking out loud here, until I have access to the docs. Thanks for your library and your help. :) Jeff