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Re: Passing functors into query: msg#00050

Subject: Re: Passing functors into query
Joel Fielder wrote:

I thought it would be cool to be able to do this instead:

query << "select whatever";
query.for_each(DoSomething());

I've added this, though I all but rewrote it for style reasons. (Yes, I'm aware that you copied the style from Query::storein_sequence(), but I didn't write that. :) )

This functionality could be added to the library (without breaking
ABI???) by adding the following into Query (plus appropriate versions
mirroring the storein functions):

I also added Query::store_if(), plus an example program to demonstrate it.

The example collects rows from the sample table with prime values in the "num" column. I'm open to ideas for a better example than primality testing. What I'm really after here is something as simple as possible, so as not to clutter the example, yet not so simple that you could write it as a WHERE clause, thus defeating the purpose.

One could argue that there should be two versions of store_if(), one for sequences and one for set type containers, but I can't really see the need. It won't take a very strong example to get me to change my mind, though, since it'd be a function naming problem down the road if we do need a version for associative containers.

I also wonder if we need support for template queries?

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