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marcelog / ex_abnf

Parser for ABNF Grammars
Apache License 2.0
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Unmatchable text: apply just returns nil? #12

Open mikebaldry opened 7 years ago

mikebaldry commented 7 years ago

Hi there,

When trying to match against invalid data, apply just seems to return nil, is there some way to generate a nicer result, perhaps where it was unable to match the next byte, at what position and what it expected and what it got?

It would be good if apply returned a standard {:ok, capture_result} or {:error, something_else}

Cheers.

Great library by the way :)

marcelog commented 7 years ago

Hi @mikebaldry,

Sure, I see your point. Take into account that nil only means that the input didn't match, and I'm not sure that something like that must be considered an error per se in any use case scenario.

Perhaps in some use cases that really is an error, but not in others. And that is something really related to how and where you are using it.

But, semantics aside, I'm open to pull requests to improve the little beast :)

Best regards!

marcelog commented 7 years ago

Another point of view: apply will return the rule that matches, while nil means: "Hey I didn't match any rules for that input, so I'm giving you nothing, zero, zip, nil. And that's cool too."

mikebaldry commented 7 years ago

I understand that point of view and it makes sense. It would be nice to know where it fell over though, mainly for debugging purposes :) I'll have a think