> However, you shouldn't be passing million-digit numbers around as (decimal) text
This is about numbers that are thousands of digits, not millions. Regardless, why not? What's the alternative that supports easy exchange? If you stick it in some hexified representation, you still have to parse text, and put it into some non-machine-native number container. It's going to be slow no matter what.
No, it's not going to be slow no matter what. Didn't you see my example? The hexadecimal non-machine-native textual representation was 4000 times faster than the decimal ditto. On a number that was much larger, I might add.
This is about numbers that are thousands of digits, not millions. Regardless, why not? What's the alternative that supports easy exchange? If you stick it in some hexified representation, you still have to parse text, and put it into some non-machine-native number container. It's going to be slow no matter what.