Re: conversion operators for UNO

On 2013-04-25 11:59, Michael Stahl wrote:
> e.g. this problem here caused a 3 % or so slowdown in ODF file load
> and/or save (i forgot which), mainly due to 2 additional queryInterface
> calls in a critical place:
> https://issues.apache.org/ooo/show_bug.cgi?id=108161
>
> with your proposal it would be possible to write code like:
>
>         Reference<B> b = ...
>         methodFooThatTakesA( b );
>         methodBarThatTakesA( b );
>         methodBazThatTakesA( b );
>
> ... and get 3 queryInterface calls instead of 1.
>
> or let me reformulate that: is it possible to implement your
> hypothetical operator such that it does not call queryInterface (i don't
> know).
Yes, I agree, it does hide the cost somewhat.
I would expect that the compilers CSE pass (common subexpression 
elimination) would reduce that to one call.

My desire is to make the UNO code less "noisy".
And it matches the natural semantics of C++, which is that it's possible 
to pass a subtype of the expected parameter's type.

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