Behaviour of Arrays

[mzuenni]

Is this intended behaviour that a variable is used like a special index in the array?
i.e. that those two programs are valid and accept:

SET(a=1)
ASSERT(INARRAY(1,a))

SET(a=1)
SET(a[1]=1)
ASSERT(!UNIQUE(a))

(My assumption would have been that a variable must either be an array or a value but not both at the same time)

[eldering]

Is this intended behaviour that a variable is used like a special index in the array? i.e. that those two programs are valid and accept:

So the way that variables and arrays at the same time are stored internally is as a map (variable name, index) -> value.

So when you call SET(a=42), then that is stored as ("a", []) -> 42, while if you call SET(a[1]=42), then that's stored as ("a", [1]) -> 42.

SET(a=1)
ASSERT(INARRAY(1,a))

So this actually checks if the value 1 exists inside the a variable for any index, including the empty list index associated to the "non-array" variable a. That's why it returns true.

SET(a=1)
SET(a[1]=1)
ASSERT(!UNIQUE(a))

Here, a contains 1 at two different indices: [] and [1], which is why UNIQUE returns false.

(My assumption would have been that a variable must either be an array or a value but not both at the same time)

I'm not arguing that this is intuitive or correct behaviour, just what is currently implemented. I think the options are either to clarify that a simple (non-array) variable is basically a special case of an array with empty index, or indeed somehow to disallow a variable to have both a non-array value (i.e. empty index) and any array values (i.e. non-empty indices) at the same time.