3 ms·

I was under the impression that C strings were inherently very fast because of how incredibly cache-friendly they are. You should not ever have to count all the

I was under the impression that C strings were inherently very fast because of how incredibly cache-friendly they are. You should not ever have to count all the bytes (memoize that!) but if you do, this is the best format there is for it.

Thiez 4y ago
What makes you say that? Besides C strings (pointer to characters, null-terminated) we have Pascal strings (pointer to length, followed by the characters), and then there is the variant that I'm not sure what it's called, that consists of a pair of (pointer, length). The last variant is my favorite, an is much nicer to use: you can take substrings without making a copy, you never have to iterate a string to find out its length, and your strings can contain the NULL character (which happens to be a perfectly normal unicode character).
- WalterBright 4y ago
  I'm not sure what it's called In D we call them dynamic arrays. They could be called length-delineated strings.
  - Thiez 4y ago
    It seems that Wikipedia refers to them as "Strings as records"[1], which I suppose fits quite well. I suppose that C strings could be considered "the most" cache friendly since it has only 1 byte overhead instead of however many bytes would be required for the length (probably 4 or 8 bytes on most modern systems). That said, I would be extremely surprised for this difference of a few bytes per string to have a measurable performance improvement in anything but an unrealistic microbenchmark involving many tiny strings. 1: https://en.wikipedia.org/wiki/String_(computer_science)#Strings_as_records https://en.wikipedia.org/wiki/String_(computer_science)#Stri...
    - WalterBright 4y ago
      0 terminated strings make sense for extremely tight memory cases, like 64Kb computers, and CPUs that don't cache memory. But they're a clear loser for 32 bit machines.
- mek6800d2 4y ago
  VAX/VMS called them "descriptors", which had IIRC 16 bits of flags, a 16-bit length, and a 32-bit pointer -- descriptors could be used for different object types, not just strings. The 64k length limit and 32-bit address were not a big issue back in 1982 when I first used them. I used (Wirth's standard) Pascal in our compiler class in college. String handling was actually pleasant in Fortran-77 on VMS, so I figured pure Pascal had the worst string handling of any language -- until I started programming in C. I finally made peace with C strings, but a couple of decades later, Forth said to me, "Here, hold my beer." I wrote some Forth-word equivalents of some of the C Library string functions to make my life a little easier! :)

Thiez 4y ago

What makes you say that? Besides C strings (pointer to characters, null-terminated) we have Pascal strings (pointer to length, followed by the characters), and then there is the variant that I'm not sure what it's called, that consists of a pair of (pointer, length). The last variant is my favorite, an is much nicer to use: you can take substrings without making a copy, you never have to iterate a string to find out its length, and your strings can contain the NULL character (which happens to be a perfectly normal unicode character).

WalterBright 4y ago
I'm not sure what it's called In D we call them dynamic arrays. They could be called length-delineated strings.
- Thiez 4y ago
  It seems that Wikipedia refers to them as "Strings as records"[1], which I suppose fits quite well. I suppose that C strings could be considered "the most" cache friendly since it has only 1 byte overhead instead of however many bytes would be required for the length (probably 4 or 8 bytes on most modern systems). That said, I would be extremely surprised for this difference of a few bytes per string to have a measurable performance improvement in anything but an unrealistic microbenchmark involving many tiny strings. 1: https://en.wikipedia.org/wiki/String_(computer_science)#Strings_as_records https://en.wikipedia.org/wiki/String_(computer_science)#Stri...
  - WalterBright 4y ago
    0 terminated strings make sense for extremely tight memory cases, like 64Kb computers, and CPUs that don't cache memory. But they're a clear loser for 32 bit machines.
mek6800d2 4y ago
VAX/VMS called them "descriptors", which had IIRC 16 bits of flags, a 16-bit length, and a 32-bit pointer -- descriptors could be used for different object types, not just strings. The 64k length limit and 32-bit address were not a big issue back in 1982 when I first used them. I used (Wirth's standard) Pascal in our compiler class in college. String handling was actually pleasant in Fortran-77 on VMS, so I figured pure Pascal had the worst string handling of any language -- until I started programming in C. I finally made peace with C strings, but a couple of decades later, Forth said to me, "Here, hold my beer." I wrote some Forth-word equivalents of some of the C Library string functions to make my life a little easier! :)