No way to check if key exists in map array in O(1)

[phobos2077]

One array opcode is missing in sfall. There is no way in O(1) to distinguish if key exists in map array or if it's a 0. The only way is to call array_key on every index which is O(n). Also the array has to be created with a "lookup" flag, without it, you can't have 0 as value in the first place.

[phobos2077]

Suggestion:

• Always allow to assign 0 value to maps.
• Add 2 new opcodes: void unset_array(OBJECT, ANY) and INT array_is_set(OBJECT, ANY) to remove key from a map and to check if key exist, respectively.
• Remove "lookup" flag (its looks like failed attempt to fix the root issue of not being able to distinguish 0).

[phobos2077]

After some more thinking, realized that there are very few cases where these opcodes are actually needed.

• Whenever you need to use array as a hashset, just use 1 as value always and you get O(1) lookups no problem.
• When you just want to store 0 value and then read it, it doesn't really matter if it's actual 0 or a function returns 0 because key doesn't exist - result is the same.
• When you need to use 0 (mostly happens when dealing with enums like damage type, many start from 0) but also need to distinguish from no-value, you can just store -1 for no-value (which is standard practice for integers in C-like languages anyway).

Case I can think of when this might be needed:

• You have an assoc. array where value can be 0
• AND, you want to use the same array as a set, to check if key exists or not

For this case, there are workarounds like:

• Store values as strings and using atoi (ugly).
• Duplicate keys in a separate array with all 1 as values (also bad).
• Whenever you set value, if it's a 0, store -1 instead (still bad).
• Initialize values with -1 and to see if value is set or not use: if (x >= 0) instead of if (x). Might not work in all cases.

But I think the case like this is somewhat rare, and you need to add 2 opcodes (or metarules) to support it. Might be overkill.