CODEWITHSUNDEEP
erlang
mipadi
mipadi

Reputation: 410662

Can I match against a string that contains non-ASCII characters?

I am writing an program in which I am dealing with strings in the form, e.g., of "\001SOURCE\001". That is, the strings contained alphanumeric text with an ASCII character of value 1 at each end. I am trying to write a function to match strings like these. I have tried a match like this:

handle(<<1,"SOURCE",1>>) -> ok.

But the match does not succeed. I have tried a few variations on this theme, but all have failed.

Is there a way to match a string that contains mostly alphanumeric text, with the exception of a non-alpha character at each end?

Upvotes: 2

Views: 129

Answers (2)

Vinod
Vinod

Reputation: 2243

You can also do the following

[1] ++ "SOURCE" ++ [1] == "\001SOURCE\001".

Or convert to binary using list_to_binary and pattern match as

<<1,"SOURCE",1>> == <<"\001SOURCE\001">>.

Upvotes: 2

zxq9
zxq9

Reputation: 13154

Strings are syntactic sugar for lists. Lists are a type and binaries are a different type, so your match isn't working out because you're trying to match a list against a binary (same problem if you tried to match {1, "STRING", 1} to it, tuples aren't lists).

Remembering that strings are lists, we have a few options:

handle([1,83,84,82,73,78,71,1]) -> ok.

This will work just fine. Another, more readable (but uglier, sort of) way is to use character literals:

handle([1, $S,$T,$R,$I,$N,$G, 1]) -> ok.

Yet another way would be to strip the non-character values, and then pass that on to a handler:

handle(String) -> dispatch(string:strip(String, both, 1)).

dispatch("STRING") -> do_stuff();
dispatch("OTHER")  -> do_other_stuff().

And, if at all possible, the best case is if you just stop using strings for text values entirely (if that's feasible) and process binaries directly instead. The syntax of binaries is much friendlier, they take up way fewer resources, and quite a few binary operations are significantly more efficient than their string/list counterparts. But that doesn't fit every case! (But its awesome when dealing with sockets...)

Upvotes: 2

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