Use pragma solidity ^

[bartleyg]

The contracts cannot currently compile when using a derived contract with pragma solidity ^0.4.24 because of the version difference and lack of the ^ in a few base contracts.

I see you are updating to solidity 0.4.24 in the cleanup branch which is very much welcome.

However, in that branch there are a few files that specify "pragma solidity 0.4.24" without the ^ carrot. Shouldn't these be "pragma solidity ^0.4.24" so that derived contracts can compile ERC777 these on future solidity versions after 0.4.24 when they come out?

[0xjac]

This was actually discussed here. Pinning the version is intentional for the implementation for safety reasons.

I will admit that recently the solidity team has been spitting out new versions very quickly and this might make sense. I need some time to think about it.