3 ms·

Reversing strings is such an odd thing to focus on. I have written dozens of implementations of string reversers for school and interviews and following books,

Reversing strings is such an odd thing to focus on. I have written dozens of implementations of string reversers for school and interviews and following books, but I would be hard pressed to come up with any real case where I needed to reverse a string. And then, it was because I was abusing a string to store some data that was not really text, at which point I really didn't care that it textually supported reversing Unicode code points.

paulmd 5y ago
rev | cut | rev is a pretty common idiom in the shell when you want to keep "all but the last N chunks" from some lines of input. At least for me. I'm sure there's probably a better way, and performance of this is definitely notably poor. And of course it's not like I'm actually writing the utility. ;)
- marcosdumay 5y ago
  I would be very surprised if rev | cut | rev gave you the correct answer to anything that isn't "drop the last X lines or words" on a non western alphabet. And for "drop the last X lines or words", you would do better with some specialized command.
  - paulmd 5y ago
    you don't ever work with directories? fortunately there is a pretty defined separator in my directory hierarchies, so that is pretty much always correct ;) (although if you are taking arbitrary user data I suppose there is nothing stopping you doing something stupid like putting an escaped '/' in a filename, which would break this.)
marcosdumay 5y ago
What is even the meaning of reversing an string? It's more meaningless the more a naive algorithm is broken... But shouldn't it at least use those reverse letters Unicode has somewhere? Or is it just a matter of putting the right to left symbol at its start?
mortoray 5y ago
It's not about reversing, but about checking whether reverse iteration works. This is required to perform proper truncation (for limited length fields) as well as visual editing for a cursor to go through the text. It can additionally be an indication as to whether regular expression matching works, though that is usually handled by a library, and not the core string types. My contention was always that if a "string" does not reverse text, then it's no better than an "array<char>". The existence of a "string" type implies it should do more.

paulmd 5y ago

rev | cut | rev is a pretty common idiom in the shell when you want to keep "all but the last N chunks" from some lines of input. At least for me. I'm sure there's probably a better way, and performance of this is definitely notably poor. And of course it's not like I'm actually writing the utility. ;)

marcosdumay 5y ago
I would be very surprised if rev | cut | rev gave you the correct answer to anything that isn't "drop the last X lines or words" on a non western alphabet. And for "drop the last X lines or words", you would do better with some specialized command.
- paulmd 5y ago
  you don't ever work with directories? fortunately there is a pretty defined separator in my directory hierarchies, so that is pretty much always correct ;) (although if you are taking arbitrary user data I suppose there is nothing stopping you doing something stupid like putting an escaped '/' in a filename, which would break this.)

marcosdumay 5y ago

What is even the meaning of reversing an string? It's more meaningless the more a naive algorithm is broken... But shouldn't it at least use those reverse letters Unicode has somewhere? Or is it just a matter of putting the right to left symbol at its start?

mortoray 5y ago

It's not about reversing, but about checking whether reverse iteration works. This is required to perform proper truncation (for limited length fields) as well as visual editing for a cursor to go through the text. It can additionally be an indication as to whether regular expression matching works, though that is usually handled by a library, and not the core string types. My contention was always that if a "string" does not reverse text, then it's no better than an "array<char>". The existence of a "string" type implies it should do more.