Consider adding a variant of memeq which reveals mismatched position

[matklad]

memeq returns a bool, but it seems sometimes it'd be useful to know the position of the mismatch.

Asked about this couple of years ago, and today was asked about this again:

https://users.rust-lang.org/t/how-to-find-common-prefix-of-two-byte-slices-effectively/25815/2

[stevenj]

This sounds more like a variant of memcmp. memcmp has to do a serial match of the byte arrays otherwise it can't return >< or =.
Memeq can use any strategy and doesn't need to be linear so the first difference it finds may not be the first difference between the arrays.

[aki-akaguma]

Thank you for your report. I'll investigate.