Compare concept

Hi guys; I just passed in the tutrials on c++ regarding to sorting on basis specific pattern and I saw like this:(forget from syntax error because I want to understand the concept behind)

Code:

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Sort(array,compare)

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Which compare is:
[code]
Compare(first,second)
{
Return (first<second)
}
[\code]
This means that the sort would be in ascending order..

What's confusing me; maybe second is the first and the first is second? So all messed up; Who said that the called function send to compare function in proper way as we thought in logic of compare?
I mean lets assume that

Code:

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arr=[5,6]

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Maybe the function send to compare second=5 ; first=6? So all thing in my logic function of compare will be messed up


Any help please?

Quote:

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Originally Posted by RyanC

Who said that the called function send to compare function in proper way as we thought in logic of compare?

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The convention says so. If someone writes a sort function that doesn't follow this convention and yet requests for a comparator of this form, then that person's sort function has a show-stopping bug.

Quote:

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Originally Posted by RyanC

Maybe the function send to compare second=5 ; first=6? So all thing in my logic function of compare will be messed up

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That's true. Maybe you should find a better function to sort your items, one that doesn't have this serious bug.

Alternatively, you could just reverse the result, but if someone could write a sort function with such a bug and not notice, what other bugs might there be?

Quote:

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Originally Posted by laserlight

The convention says so. If someone writes a sort function that doesn't follow this convention and yet requests for a comparator of this form, then that person's sort function has a show-stopping bug.


That's true. Maybe you should find a better function to sort your items, one that doesn't have this serious bug.

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so if I understand you, I make my compare as my assumptions ! and search for any other sort functions that's suitable to my assumption/logic of compare that I built?

A more sensible approach would be to look at what are the requirements for the comparator of whatever generic sort function you want to use.

thanks alot!