In Scratch 2.0, support for custom stack blocks (procedures) was added. But is there any way to use this to "abstract away" logic that returns a value?
For example, i have here a script to naively calculate exponents: (view graphic representation)
set [base v] to [2]
set [index v] to [3]
... // above is for initializing
set [result v] to (base)
repeat until <(index) = [1]>
set [result v] to ((result) * (base))
change [index v] by (-1)
How could i export this logic to a "custom reporter" to reuse?
The easiest way to do this is by creating a custom command block, and storing the return value in a variable. This has some drawbacks, such as not allowing recursive calls, but works in most cases. I also recommend setting the block to run without screen refresh.
Simply define it like this, with the return value available as result:
define (base) ^ (exp)
set [index v] to (exp) // need a variable, as arguments are immutable
set [result v] to (base)
repeat until <(index) = [1]>
set [result v] to ((result) * (base))
change [index v] by (-1)
It can then be called like:
when gf clicked
(4) ^ (3) // the stack block
say (join [4 ^ 3 = ] (result)) // result is set by the [()^()] block