len function doesn't work on static arrays

[fubuloubu]

It should be possible to ask for the length of a static array, and have it give you the same number back you used to set it up

def balanceOfBatch(accounts: address[50], ids: uint256[50]) -> uint256[100]:
    assert len(accounts) == len(ids), "ERC1155: accounts and ids length mismatch"

but tells me that len only function for bytes and string types

Originally posted by @QuetzalAzul in #2346

[iamdefinitelyahuman]

This can be handled pretty easily during constant folding. Although given the length of an array is static, it seems redundant?

[fubuloubu]

Although given the length of an array is static, it seems redundant?

It would be sort of redundant, but it would be a handy shortcut that's easier to read versus having to go check that the sizes match of two static arrays. It also introduces syntax that will become handy with dynamic arrays.

[charles-cooper]

@fubuloubu What should len return, size in bytes, words or elements?

[fubuloubu]

@fubuloubu What should len return, size in bytes, words or elements?

Number of elements of the list, basically SomeType[N] should just be N

[charles-cooper]

@fubuloubu can we close this as dup of #1963?

[fubuloubu]

I wouldn't say a dup of it, the two functions perform different roles, but yes they are related