Question

I’ve been playing around with searching text in big lists and found that using a PHP array seems to be a quick way of doing it.

E.g. if you had loads of place names and associated postcodes you could read them into a PHP array like this:

$place[‘place name here’] = “postcode”;

Then to look up you just take the place you want to look up and plug it in to the array:

$postcode_sought = $place[‘place I want to look up’];

I thought I could speed this up using C++ but of course C++ does not allow (as far as I know) arrays with a string as the index.

The only way I can think to do it is to create vectors for the place and postcode and loop through the place vector looking for a match but the repeated string comparisons take forever as I’d expected. I also experimented with hashing the text but I still couldn’t get it anywhere near as fast as PHP.

I think PHP is written in C so my question is how does C manage to create this string index name functionality for PHP?
I’m not looking for the actual code or anything, it just seems to me that there must be some fundamental technique that is used for this and I was just wondering if there is anyone out there who could briefly explain it.

Thanks in advance.
C

Answer 1

I thought I could speed this up using C++ but of course C++ does not allow (as far as I know) arrays with a string as the index.

It does, You can use std::map as an Associative array.