On 2017-08-18 15:53, Mike Kerner via use-livecode wrote:
I understand the difference. I'm just trying to help with the mental
arithmetic. I, and others, I'm sure, will constantly forget where the
"@"
goes, for instance.
Okay so - the question to ask is - what would make you forget where to
put the "@"?
In this case, if you want a by-ref parameter you have to put '@' before
it in the signature, the proposal is to allow '@' to also be placed
before the argument in a handler call for by-ref parameters... So it is
entirely symmetric:
command myHandler @xFoo
end myHandler
myHandler @tFoo
There is no 'de-referencing' operation as by-ref parameters implicitly
de-reference on use - indeed, there's no need to have a de-reference
operation because there is no such thing as a 'reference' which can be
'put into' a variable (that would be general references - which this
isn't about).
In fact, what is happening is aliasing of variables:
myHandler @tFoo -- when tFoo is passed to myHandler, xFoo1 in
myHandler is aliased to tFoo
command myHandler @xFoo1 -- xFoo1 as a variable does not exist, it is
an alias to the calling var
myOtherHandler @xFoo -- xFoo *is* tFoo, we are passing by-ref again
so use @ which 'passes the alias on'
end myHandler
command myOtherHandler @xFoo2 -- xFoo2 as a variable does not exist,
it is an alias to the calling var
answer xFoo2 -- xFoo2 *is* tFoo
end myOtherHandler
Perhaps I'm not explaining this very well - or there is something I'm
missing...
Warmest Regards,
Mark.
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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