Guessing game

David Bovill david.bovill at gmail.com
Tue Apr 3 04:28:11 EDT 2018


Arrays as first class citizens? Give them a passport! Arrays have rights
too!

Need to check if they can be passed as parameters in setprop handlers - as
in “set the beautiful_Colour [spellingArray] of my card to light-grey”

Last time I checked not all first class citizens were equal.

On Tue, 3 Apr 2018 at 08:51, Mark Waddingham via use-livecode <
use-livecode at lists.runrev.com> wrote:

> On 2018-04-02 21:28, J. Landman Gay via use-livecode wrote:
> > I found this:
> >
> > ***
> > Additionally the into clause has been added to all array set set
> > operations allowing commands such as:
> >
> >   intersect tLeft with tRight into tResult
> >
> > The operation of the commands is the same as the non-into form except
> > that tLeft does not have to be a variable, and the result of the
> > operation is placed into tResult rather than mutating tLeft.
> > ***
> >
> > So when is an array not a variable?
>
> I must confess I found this quite an interesting question - as it speaks
> to the history of arrays in LiveCode.
>
> Originally there were no arrays 'just' variables - a variable could hold
> a string, nothing else.
>
> Then arrays were added, but they were not 'first class citizens' - so a
> perfectly reasonable mental model was that variables had been augmented
> so that they could be collections of named variables - each holding a
> string. (e.g. tFoo["a"], tFoo["b"] were both distinct variables, just
> with a convenient/indexable way of referencing them, and passing them
> around as a collection).
>
> However, this changed when we added hierarchical arrays - i.e. being
> able to set an array as the value of an array key. The variable centric
> model then doesn't work so well - it is perhaps 'better' to think of
> arrays as values like strings. i.e. Arrays ceased to be tied to the
> notion of variable at all, and just became a 'value' which can be put
> into a variable.
>
> Personally I think I always thought of arrays in LiveCode as values, but
> ones which had only been 'partially implemented' - there were lots of
> places prior to adding hierarchical arrays which wouldn't work with the
> existing notion of array, but had to be made to for hierarchical arrays
> to be in any way useful.
>
> Another way to think about 'into' being added to intersect/union is that
> we've essentially added binary operators for array union and intersect:
>
>    intersect tLeft with tRight into tResult
>
> Does the same thing as a hypothetical 'intersect' binary operator:
>
>    put tLeft intersect tRight into tResult
>
> One could imagine a similar thing being added to the arithmetic
> commands:
>
>    add tLeft to tRight into tResult
>
> Would do nothing different from:
>
>    put tLeft + tRight into tResult
>
> This would just be a different way of expressing the same thing
> syntactically. (Note the 'into' form has not been added to the
> arithmetic commands, and there is no binary intersect/union operator -
> but perhaps both should be considered).
>
> Warmest Regards,
>
> Mark.
>
> --
> Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
> LiveCode: Everyone can create apps
>
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