VIP: extract32 should be able to output types: decimal, int128, uint256, address or bytes32

[brockelmore]

Simple Summary

We shouldn't have to use convert when we are using extract32 to get currently unsupported return types.

Abstract

Currently, extract32 only supports bytes32, int128, and address as output types - if we are going to have type conversions integrated into this, we should allow for all supported conversions. Currently, if we want decimal, or uint256, we have to wrap the extract32 in a convert(extract32(byteArr, start, bytes32), uint256).

Motivation

This improves code readability.

Specification

The following should work:

extract32(byteArr, start, type=uint256)

extract32(byteArr, start, type=decimal)

Where extract32:

def extract32(a, b, type=c) -> d:
  """
  :param a: where 32 bytes are extracted from
  :type a: bytes
  :param b: start point of bytes to be extracted
  :type b: int128
  :param c: type of output (Optional, default: bytes32)
  :type c: either bytes32, int128, address, uint256, or decimal

  :output d: either bytes32, int128, address, uint256, or decimal
  """

I think this could be achieved by just implementing convert into the underlying code https://github.com/ethereum/vyper/blob/f890abe1907d9c4329950c400f348f9102a5263b/vyper/functions/functions.py#L553 in this area, instead of manually doing this.

Totally open to this idea being dumb, and definitely dont understand everything as I am relatively new to the repo.

Backwards Compatibility

Not totally sure

Dependencies

Copyright

Copyright and related rights waived via CC0

[charles-cooper]

related: #1093