On 2015-10-27 10:22, Monte Goulding wrote:
On 27 Oct 2015, at 8:02 pm, Mark Waddingham <m...@livecode.com> wrote:
Note that in all three 'operator' cases, you can also have expressions
in-between the tokens:
<Expression> 'is' 'between' <Expression> 'and' <Expression>
Out of interest if I implement the above syntax but only for
expressions that evaluate to a number can someone else implement it
for expressions that evaluate to strings or some other thing. Can the
be used together by some other user that doesn’t care about the
implementation detail?
There are two ways to interpret your question...
Option (1):
Person A: x OP y => EvalOP(in x as integer, in y as integer) returns
array
Person B: x OP y => EvalOP(in x as string, in y as string) returns
boolean
Option (2):
Person A: x OP y => EvalOP(in x as integer, in y as integer) returns
integer
Person B: x OP y => EvalOP(in x as integer, in y as integer) returns
string
The difference here is that in Option (1), you can have differing return
types as long as the types of the parameters are different. In Option
(2), you can have differing return types even if the types of the
parameters are the same.
Open Language definitely allows Option (1) - it is the basis of how
'specialization' of syntax can work for different argument types. This
model is one where 'types flow downward' to work out how which variant
to call.
Now, Option (2) is quite different - it means that the context of the
use of an expression can be used to choose which form to call. This
could work with the type-system in LiveCode Builder - I doubt it could
be made to work effectively in LiveCode Script, too many ambiguities
would arise (as the type required in a given context in LiveCode Script
is often flexible).
That being said Option (2) is a proper superset of functionality for
Option (1) so it is something we can explore at a later date. From all
the work I have done up until now, Option (1) appears to be more than
sufficient a model for currently existing LiveCode Script, and the
purposes LiveCode Builder is currently being put to.
Warmest Regards,
Mark.
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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