Contains vs is in

[Ali Lloyd]

As an example, consider a list ["a", "b", "c"]. "a" is in the list. But the
list ["a", "b"] is *not* in the list, as it is not an element of the list -
all the elements of the list are strings, and ["a", "b"] is a list.
However, ["a", "b", "c"] *does* contain ["a", "b"] as the latter occurs as
a 'substring' (in the sense of the wikipedia links I posted).

On Wed, Jan 4, 2017 at 1:39 PM Mike Kerner <MikeKerner at roadrunner.com>
wrote:

> WHAT?
> There is some subtlety that I am missing, Ali.
>
> On Wed, Jan 4, 2017 at 5:22 AM, Ali Lloyd <ali.lloyd at livecode.com> wrote:
>
> > Peter has pointed out that I am technically using the word 'subsequence'
> in
> > error, and should probably have used 'substring' instead!
> > (cf https://en.wikipedia.org/wiki/Subsequence vs
> > https://en.wikipedia.org/wiki/Substring)
> >
> > On Wed, Jan 4, 2017 at 10:16 AM Ali Lloyd <ali.lloyd at livecode.com>
> wrote:
> >
> > > 'contains' and 'is in' are implemented exactly the same in LiveCode
> > > Script, so there shouldn't be any difference. However there is an
> > > interesting subtlety that emerges when you consider what these two bits
> > of
> > > syntax should do, which explains why they are different in LCB.
> > >
> > > When we say 'A contains B' where A is some sort of sequence (ordered
> > set),
> > > then I would argue we really mean that B is a subsequence of A. On the
> > > other hand I think the interpretation of 'is in' is the same as that of
> > 'is
> > > among the elements of'.
> > >
> > > Thus 'contains' is actually a relation between sequences and sequences,
> > > whereas 'is in' is one between elements and sequences. This makes no
> > > difference in LCS for strings because the type of the sequence is the
> > same
> > > as the type of the element, namely they are strings. However it does
> mean
> > > that the following two should be considered anomalous:
> > >
> > > 1) In LCS, 'is in' does not restrict the left hand side to a single
> char
> > > 2) In LCS, no string other than empty 'contains' empty
> > >
> > > Both of these anomalies are rectified in LCB. The situation becomes
> > > clearer when using an LCB list, where <list> contains <string> is a
> > syntax
> > > error, and <listA> is in <listB> is only true if listA occurs as an
> > > *element* of listB, rather than a subsequence. Moreover <list> contains
> > []
> > > is always true.
> > >
> > >
> > > tl;dr - there should be no performance difference between 'contains'
> and
> > > 'is in' in LCS.
> > >
> > >
> > > On Tue, Jan 3, 2017 at 11:35 PM Bob Sneidar <
> bobsneidar at iotecdigital.com
> > >
> > > wrote:
> > >
> > > I interact with copier interfaces quite a lot and the process of
> backing
> > > up the data involves going through various pages and typing what I see
> > > there into a text file. I have always thought it would be great to
> write
> > an
> > > app that can do it for me, but I have never been able to scrape
> anything
> > > more than the HTML text displayed on the page.
> > >
> > > I will have to look into ways to use Javascript to do it. If it
> requires
> > > already knowing what the values are though, I'm afraid I might meet
> with
> > > unsurpassable difficluty.
> > >
> > > Bob S
> > >
> > >
> > > On Jan 3, 2017, at 15:02 , Mike Kerner <MikeKerner at roadrunner.com<
> > mailto:
> > > MikeKerner at roadrunner.com>> wrote:
> > >
> > > the short answer is "yes", but it can be more complicated as it may
> > require
> > > some javascript execution to pull the data from the server.  It depends
> > on
> > > the site you are scraping.  You can also (possibly) use a service that
> > can
> > > yank that for you.
> > >
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