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Comment by omgitsabird | Hacker News Reader

Is copilot just a search engine over function and variable names with some filters and transformers (like a transcompiler)?

I just got into the preview today, and it seems like that is what it is to me.

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It's not. It's basically the same model as GPT-3 (though smaller), and generally speaking the vast majority of its outputs should not be anything in its training set. The big exception is code that showed up many times in the training data (like the famous inverse square root function).

It is based on a machine learning model. I've been using it for a couple of months now and the suggestions are generally speaking surprisingly good. It has been able to usefully complete very obscure things, like parts of a PEG grammar for parsing Quake-C. I'm not using it to generate implementations of algorithms from scratch (because it just doesn't have enough data to do that properly), but rather as a fancy extension of regular code completion.

I imagine being offered complex code completion can lead to just accept it at times, without understanding it fully and therefore lots of potential for hidden bugs. Did you notice anything like this?

It is quite rare, but happens sometimes. You basically have to explicitly ask for a complex completion by writing a specification in a comment. Normally it tends to just complete a single statement or other syntax element at a time, which are usually easy to read and pretty close to correct.

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