3 ms·

> You're talking about strings here, right? This is not true in all languages, but certainly is for C :) It costs O(1) in memory to delimit strings with a null

> You're talking about strings here, right? This is not true in all languages, but certainly is for C :) It costs O(1) in memory to delimit strings with a null terminator and O(n) in time to execute strnlen(), right? It's not free. Though, if you're lucky your string is in rodata and the compiler can calculate the sizeof() in advance, this is very-nearly-free. EDIT: misunderstanding, disregard

steveklabnik 8y ago
Only if your strings are null terminated; many languages do not use null termination for various reasons, and that's one of them. "Pascal strings" being the nickname, given how old this idea is, and given it was a direct competitor to C at the time.
- wyldfire 8y ago
  > > You really should understand how things like .size or lengh() aren’t “free” and how they work. > You're talking about strings here, right? This is not true in all languages, but certainly is for C :) I realize now that I misread this. It sounded as if you were saying '...but it is [free] for C', and on re-read I now understand that's not what you said at all.
  - steveklabnik 8y ago
    Ah, no worries! I've edited it to make it more clear, hopefully.
hawkice 8y ago
Right. But some languages prefix the string data with its length and omit the null terminator. So, depending on if the struct is passed in registers, you could say .length is free, in that it wouldn't even need a load.
GolDDranks 8y ago
That assumes that all strings are C strings which isn't true. For example, Pascal-style strings have a size before the string data, and Rust and C++ strings have the size as metadata on stack and the string data in heap.
- steveklabnik 8y ago
  This thread apparently started out as a misunderstanding, but just to show how free this can be: https://godbolt.org/z/7ehDPx https://godbolt.org/z/7ehDPx
  - GolDDranks 8y ago
    I think you replied to the wrong post! (Thanks for the nice article btw.)
    - steveklabnik 8y ago
      Gah, you're right. Too many tabs. Thanks and you're welcome :)

steveklabnik 8y ago

Only if your strings are null terminated; many languages do not use null termination for various reasons, and that's one of them. "Pascal strings" being the nickname, given how old this idea is, and given it was a direct competitor to C at the time.

wyldfire 8y ago
> > You really should understand how things like .size or lengh() aren’t “free” and how they work. > You're talking about strings here, right? This is not true in all languages, but certainly is for C :) I realize now that I misread this. It sounded as if you were saying '...but it is [free] for C', and on re-read I now understand that's not what you said at all.
- steveklabnik 8y ago
  Ah, no worries! I've edited it to make it more clear, hopefully.

hawkice 8y ago

Right. But some languages prefix the string data with its length and omit the null terminator. So, depending on if the struct is passed in registers, you could say .length is free, in that it wouldn't even need a load.

GolDDranks 8y ago

That assumes that all strings are C strings which isn't true. For example, Pascal-style strings have a size before the string data, and Rust and C++ strings have the size as metadata on stack and the string data in heap.

steveklabnik 8y ago
This thread apparently started out as a misunderstanding, but just to show how free this can be: https://godbolt.org/z/7ehDPx https://godbolt.org/z/7ehDPx
- GolDDranks 8y ago
  I think you replied to the wrong post! (Thanks for the nice article btw.)
  - steveklabnik 8y ago
    Gah, you're right. Too many tabs. Thanks and you're welcome :)