Subject: Re: [erlang-questions] List Question

A string is a list of integers [$F, $T] (where $x is a code for the letter x and so on)A list of strings is a — List of lists of integers. That is [ [$F, $T], [$S, $T] ]So to check whether a value is a list of lists you take its first element and check whether it's also a list
function([X | _] = List) when is_list(X) -> got a nonempty list of strings!function([X | _]) when is_list(X) -> got a nonempty list of integers (one string)function([]) -> i am sorry, empty list is here
there is no way to know having an empty list what it supposed to contain. So an empty list is an empty list
2017-08-07 14:13 GMT+02:00 Andrew McIntyre <[email protected]>:
Hello All,

A Newbie question,

Can I tell the difference Between a List of Strings and a Single

eg the Value in a List may just be "FT" or it might be ["FT", "ST"]

I do not know in advance if its a single string or a list of strings,
but want to behave differently - actually return the first element of
the list when there are multiple values. I have parsed a variable
hierarchical structure and the hierarchy can vary over instances.

As strings are lists "is_list" returns true for both. Is that soluble
or do I need to change the data structure to indicate it. Sorry if
this has obvious answer, but new to erlang.


Best regards,
Andrew McIntyre                     mailto:[email protected]

sent from a real computer

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